The term acute abdomen defines a clinical syndrome characterized by the sudden onset of severe abdominal pain requiring emergency medical or surgical treatment. It is one of the most frequent reasons for presentation of an adult to the emergency department, ranging from 4% to 10% of admissions. A prompt and accurate diagnosis is essential to minimize morbidity and mortality in these patients. The differential diagnosis includes a spectrum of infectious, inflammatory, ischemic, obstructive, hemorrhagic, and neoplastic disorders. The acute abdomen can also reflect extra-abdominal conditions, including cardiac, pulmonary, endocrine, or metabolic disorders.

1. Imaging of Acute Abdomen
Dr Abhineet Dey
Department of Radiology, Silchar Medical College & Hospital (SMCH)

2. Imaging of non-
traumatic acute
abdomen
• Acute abdomen
• Imaging modalities
• Abdominal regions:
 Right upper quadrant (RUQ) pain
 Left upper quadrant (LUQ) pain
 Epigastric pain
 Right lower quadrant (RLQ) pain
 Left lower quadrant (LLQ) pain
 Non-localized acute abdominal pain
• Conclusion
Outline

3. Acute abdomen
Acute abdominal pain in a subgroup of patients who are seriously ill and
have abdominal tenderness and rigidity.

4. Diagnostic conundrum
• The differential diagnosis for abdominal pain is broad, encompassing
gastrointestinal, gynecologic, urologic, vascular, and musculoskeletal conditions.
• A confident and accurate diagnosis can be made solely on the basis of medical
history, physical examination, and laboratory test findings in only a small
proportion of patients.
• The clinical manifestations of the various causes of acute abdominal pain usually
are not straightforward.
• For proper treatment, a diagnostic work-up that enables the clinician to
differentiate between the various causes of acute abdominal pain is important, and
imaging plays an important role in this process.

5. ACR Appropriateness Criteria
• Evidence-based guidelines to help physicians make the most appropriate
imaging decisions for specific clinical conditions.
• The ACR Appropriateness Criteria for abdominal imaging are based primarily on
the location of pain. For most locations, the ACR provides several clinical
variants (e.g., presence or absence of fever, leukocytosis, pregnancy) and outlines
the appropriate imaging for each scenario.
• This presentation includes one clinical variant for each pain location; tables for all
clinical variants are available at https://acsearch.acr.org/list

6. Imaging modalities
Imaging plays an important role in the management of patients because
clinical evaluation results can be inaccurate.

7. Conventional radiography
• Conventional radiography is commonly the initial imaging examination performed
in the diagnostic work-up of patients who present with acute abdominal pain to the
ED.
• This examination is widely available, can be easily performed in admitted patients,
and is used to exclude major illness such as bowel obstruction and perforated
viscus.
• Conventional radiography includes supine and upright conventional abdominal
radiography and upright chest radiography.

8. Conventional radiography
• The accuracy values for conventional
radiography in the diagnostic work-up of
patients with acute abdominal pain are
not convincing.
• However, it is widely available in the
ambulatory setting and is often the initial
imaging test for evaluation of outpatients
with abdominal pain.
• Conventional radiography has been
reported to have good accuracy in the
following conditions however:
• Bowel obstruction
• Perforated viscus
• Urinary tract calculi
• Foreign bodies
In a recent study*, however, only the
sensitivity for the diagnosis of bowel
obstruction was significantly higher after
conventional radiograph evaluation
* van Randen A, Lameris W, Bossuyt PM, Boermeester MA, Stoker J. Comparison of accuracy of ultrasonography and computed tomography in patients
with acute abdominal pain at the emergency department [abstr]. In: Radiological Society of North America scientific assembly and annual meeting
program. Oak Brook, Ill: Radiological Society of North America, 2009; 519.

9. Ultrasonography (USG)
• US is another imaging modality commonly used in the diagnostic work-up of
patients with acute abdominal pain.
• With US, the abdominal organs and the alimentary tract can be visualized. Curved
(3.5–5.0-MHz) and linear (5.0–12.0-MHz) transducers are used most commonly,
with frequencies depending on the application and the patient’s stature
• Graded-compression procedure: Interposing fat and bowel can be displaced or
compressed by means of gradual compression to show underlying structures. This
is the most common US technique used to examine patients with acute abdominal
pain
• Furthermore, if the bowel cannot be compressed, the non-compressibility itself is
an indication of inflammation.

10. Ultrasonography (USG)
Advantages
• Wide availability in the ED
• Lower costs
• Absence of radiation exposure
• Real-time dynamic examination: Can
reveal presence/absence of peristalsis
and depict blood flow
• Clinical tool: US findings can correlate
with the point of maximal tenderness.
Disadvantages
• Operator dependent
• Patient dependent: Patient body
habitus, cooperation
• Bowel gas shadow can obscure findings

11. Computed tomography (CT)
• The CT technique used to examine patients with acute abdominal pain generally
involves scanning of the entire abdomen after intravenous administration of an
iodinated contrast medium
• Although rectal or oral contrast material may be helpful in differentiating fluid-
filled bowel loops from abscesses in some cases, the use of oral contrast material
can markedly increase the time these patients spend in the ED. *
* Huynh LN, Coughlin BF, Wolfe J, Blank F, Lee SY, Smithline HA. Patient encounter time intervals in the evaluation of emergency department
patients requiring abdominopelvic CT: oral contrast versus no contrast. Emerg Radiol 2004;10:310–313.

12. Computed tomography (CT)
• Exposure to ionizing radiation is a disadvantage of CT.
• The effective radiation dose for abdominal CT is approximately 10 mSv. In
comparison, the annual background radiation dose in the United States is
approximately 3 mSv.
• A 10-mSv CT examination performed in a 25-year old person is associated with an
estimated risk of induced cancer of one in 900 individuals and a risk of
induced fatal cancer of about one in 1800 individuals*. For older individuals,
these risks are considerably lower. These risks should be weighed against the direct
diagnostic benefit and related to the lifetime cancer risk
* The 2007 recommendations of the International Commission on Radiological Protection. ICRP publication 103. Ann ICRP 2007; 37:1–332.

13. Magnetic resonance (MR)
• MR imaging has demonstrated promising accuracy for the assessment and
diagnosis of appendicitis, albeit in a relatively small series of patients, who often
were pregnant. MR imaging is also accurate in the diagnosis of diverticulitis. MR
imaging is more accurate than CT for the diagnosis of acute cholecystitis and the
detection of common bile duct stones.
• At this time, MR imaging is used in only select cases at many institutions, primarily
after US yields nondiagnostic findings in pregnant women.
• MR imaging has contraindications, including claustrophobia, which may prevent
MR imaging from being performed.
* Oto A. MR imaging evaluation of acute abdominal pain during pregnancy. Magn Reson Imaging Clin N Am 2006;14:489–501. 35.
* Oh KY, Gilfeather M, Kennedy A, et al. Limited abdominal MRI in the evaluation of acute right upper quadrant pain. Abdom Imaging 2003;28:643–651. 36.
* Aube C, Delorme B, Yzet T, et al. MR cholangiopancreatography versus endoscopic sonography in suspected common bile duct lithiasis: a prospective,
comparative study. AJR Am J Roentgenol 2005;184:55–62. 37.
* Stoker J. Magnetic resonance imaging and the acute abdomen. Br J Surg 2008;95: 1193–1194.

14. Imaging
Recommendations
Imaging Recommendations for
Evaluating Select Causes of Acute
Abdominal Pain in Adults
Cartwright, S. L., & Knudson, M. P. (2015).
Diagnostic imaging of acute abdominal pain in
adults. American family physician, 91(7), 452–
459.

15. Right Upper Quadrant
Ultrasonography (US) is the imaging examination of choice for evaluation of
acute right upper quadrant pain.

16. ACR Appropriateness Criteria
Initial imaging of right upper quadrant (RUQ) pain
Expert Panel on Gastrointestinal Imaging, Russo, G. K., Zaheer, A., Kamel, I. R., Porter, K. K., Archer-Arroyo, K., Bashir, M. R., Cash, B. D., Fung, A.,
McCrary, M., McGuire, B. M., Shih, R. D., Stowers, J., Thakrar, K. H., Vij, A., Wahab, S. A., Zukotynski, K., & Carucci, L. R. (2023). ACR Appropriateness
Criteria® Right Upper Quadrant Pain: 2022 Update. Journal of the American College of Radiology : JACR, 20(5S), S211–S223.
https://doi.org/10.1016/j.jacr.2023.02.011

17. Acute cholecystitis
• Acute cholecystitis is a primary diagnostic consideration in patients presenting
with new-onset right upper quadrant pain.
• The prevalence of acute cholecystitis is approximately 5% in patients who present
with acute abdominal pain to the ED.
• Diagnostic clinical triad:
1. Right upper quadrant tenderness
2. Elevated body temperature
3. Elevated WBC count
However, this triad was present in only 8% of patients in a prospective series
* Lameris W, van Randen A, Ten Hove W, Bossuyt PM, Boermeester MA, Stoker J. The clinical diagnosis of acute cholecystitis is unreliable
[abstr]. In: Radiological Society of North America Scientific Assembly and Annual Meeting Program. Oak Brook, Ill: Radiological Society of
North America, 2008;110.

18. Tokyo Guidelines 2018/2013 (TG18/TG13)
A. Local signs of inflammation:
1. Murphy's sign
2. RUQ mass/pain/tenderness
B. Systemic signs of inflammation:
1. Fever
2. Elevated CRP
3. Elevated WBC count
C. Imaging findings: Imaging findings characteristic of acute cholecystitis
• Suspected diagnosis: One item in A + one item in B
• Definite diagnosis: One item in A + one item in B + C

19. Acute cholecystitis: USG
According to ACR appropriateness criteria, US is considered the most appropriate
imaging modality for patients suspected of having acute calculous cholecystitis.
FINDINGS:
• Sonographic Murphy sign (tenderness elicited by pressing the gallbladder with
the ultrasound probe)
• Thickened gallbladder wall (>4 mm; if the patient does not have chronic liver
disease and/or ascites or right heart failure)
• Enlarged gallbladder (long axis diameter > 8 cm, short axis diameter > 4 cm)
• Incarcerated gallstone, debris echo, pericholecystic fluid collection
• Sonolucent layer in the gallbladder wall, striated intramural lucencies, and
Doppler signals.

20. Typical ultrasound images of acute cholecystitis. (a) Pericholecystic fluid. Pericholecystic fluid is demonstrated to the
left side of the gallbladder. Gallstones and debris are also seen in the gallbladder. (b) An intraluminal flap seen in a
gangrenous cholecystitis. A linear echogenic line representing the intraluminal flap is demonstrated
Yokoe, M., Hata, J., Takada, T., Strasberg, S.M., Asbun, H.J., Wakabayashi, G., Kozaka, K., Endo, I., Deziel, D.J., Miura, F., Okamoto, K., Hwang, T.-L., Huang, W.S.-W.,
Ker, C.-G., Chen, M.-F., Han, H.-S., Yoon, Y.-S., Choi, I.-S., Yoon, D.-S., Noguchi, Y., Shikata, S., Ukai, T., Higuchi, R., Gabata, T., Mori, Y., Iwashita, Y., Hibi, T., Jagannath,
P., Jonas, E., Liau, K.-H., Dervenis, C., Gouma, D.J., Cherqui, D., Belli, G., Garden, O.J., Giménez, M.E., de Santibañes, E., Suzuki, K., Umezawa, A., Supe, A.N., Pitt, H.A.,
Singh, H., Chan, A.C.W., Lau, W.Y., Teoh, A.Y.B., Honda, G., Sugioka, A., Asai, K., Gomi, H., Itoi, T., Kiriyama, S., Yoshida, M., Mayumi, T., Matsumura, N., Tokumura,
H., Kitano, S., Hirata, K., Inui, K., Sumiyama, Y. and Yamamoto, M. (2018), Tokyo Guidelines 2018: diagnostic criteria and severity grading of acute cholecystitis
(with videos). J Hepatobiliary Pancreat Sci, 25: 41-54. https://doi.org/10.1002/jhbp.515

21. Typical ultrasound images of acute cholecystitis. (a) Color Doppler images of acute cholecystitis. Increased
intraluminal blood flow is demonstrated. However, it is not always easy to estimate the intraluminal flow since the sensitivity
of color Doppler imaging is influenced by several factors such as the settings of the filter, velocity range, frequency of the
ultrasound beam, the patients’ constitutions, and the limitations of the equipment. (b) Superb Microvascular Imaging of acute
cholecystitis. Superb Microvascular imaging, which is more sensitive than the conventional color Doppler in the detection
of blood flow, shows the increased intraluminal flow of the gallbladder in a patient with acute cholecystitis. Still, the same
problem as described in the figure legend of (a) remains so it is difficult to make use of these Doppler imagings as an
objective method for the diagnosis of acute cholecystitis
Yokoe, M., Hata, J., Takada, T., Strasberg, S.M., Asbun, H.J., Wakabayashi, G., Kozaka, K., Endo, I., Deziel, D.J., Miura, F., Okamoto, K., Hwang, T.-L., Huang, W.S.-W.,
Ker, C.-G., Chen, M.-F., Han, H.-S., Yoon, Y.-S., Choi, I.-S., Yoon, D.-S., Noguchi, Y., Shikata, S., Ukai, T., Higuchi, R., Gabata, T., Mori, Y., Iwashita, Y., Hibi, T., Jagannath,
P., Jonas, E., Liau, K.-H., Dervenis, C., Gouma, D.J., Cherqui, D., Belli, G., Garden, O.J., Giménez, M.E., de Santibañes, E., Suzuki, K., Umezawa, A., Supe, A.N., Pitt, H.A.,
Singh, H., Chan, A.C.W., Lau, W.Y., Teoh, A.Y.B., Honda, G., Sugioka, A., Asai, K., Gomi, H., Itoi, T., Kiriyama, S., Yoshida, M., Mayumi, T., Matsumura, N., Tokumura,
H., Kitano, S., Hirata, K., Inui, K., Sumiyama, Y. and Yamamoto, M. (2018), Tokyo Guidelines 2018: diagnostic criteria and severity grading of acute cholecystitis
(with videos). J Hepatobiliary Pancreat Sci, 25: 41-54. https://doi.org/10.1002/jhbp.515

22. Acute cholecystitis: CT
CT findings
• Thickened gallbladder wall
• Pericholecystic fluid collection
• Enlarged gallbladder
• Linear high-density areas in the
pericholecystic fat tissue
Complications
• Perforation/abscess formation,
• Hemorrhage
• Gas (in diabetic patients with
emphysematous cholecystitis)
• Wall gangrene
Computed tomography (CT) is not used for the initial evaluation of right upper quadrant pain.
It may be considered in patients with inconclusive ultrasonography or cholescintigraphy
results or to help guide surgical planning.

23. Typical computed tomography (CT) images of gangrenous cholecystitis. Woman in her 70s with gangrenous
cholecystitis (acute acalculous cholecystitis). Dynamic contrast-enhanced CT (a, plain; b, early phase; c, equilibrium phase).
Enlargement of the gallbladder, thickening of the gallbladder wall, and edematous lesions beneath the gallbladder
serosa are evident on plain CT (arrows). On contrast-enhanced CT (b,c), irregularity of the gallbladder wall and the
partial lack of contrast enhancement can be seen (arrows) as the characteristic appearance of gangrenous cholecystitis.
Transient early-phase staining of the hepatic parenchyma (b) and edematous changes to the hepatoduodenal
ligament (c, arrowhead) are also apparent, suggesting the spread of inflammation
Yokoe, M., Hata, J., Takada, T., Strasberg, S.M., Asbun, H.J., Wakabayashi, G., Kozaka, K., Endo, I., Deziel, D.J., Miura, F., Okamoto, K., Hwang, T.-L., Huang, W.S.-W.,
Ker, C.-G., Chen, M.-F., Han, H.-S., Yoon, Y.-S., Choi, I.-S., Yoon, D.-S., Noguchi, Y., Shikata, S., Ukai, T., Higuchi, R., Gabata, T., Mori, Y., Iwashita, Y., Hibi, T., Jagannath,
P., Jonas, E., Liau, K.-H., Dervenis, C., Gouma, D.J., Cherqui, D., Belli, G., Garden, O.J., Giménez, M.E., de Santibañes, E., Suzuki, K., Umezawa, A., Supe, A.N., Pitt, H.A.,
Singh, H., Chan, A.C.W., Lau, W.Y., Teoh, A.Y.B., Honda, G., Sugioka, A., Asai, K., Gomi, H., Itoi, T., Kiriyama, S., Yoshida, M., Mayumi, T., Matsumura, N., Tokumura,
H., Kitano, S., Hirata, K., Inui, K., Sumiyama, Y. and Yamamoto, M. (2018), Tokyo Guidelines 2018: diagnostic criteria and severity grading of acute cholecystitis
(with videos). J Hepatobiliary Pancreat Sci, 25: 41-54. https://doi.org/10.1002/jhbp.515

24. Emphysematous
Cholecystitis
Plain-film radiography showing air in
the lumen and wall of the enlarged
gallbladder of a 64-year-old woman
with abdomen pain and shock while
undergoing hemodialysis (arrows)

25. Emphysematous Cholecystitis
(A) Coronal CT—intramural gas (arrows); (B) US—intraluminal gas appears as a bright curvilinear echogenic
band (arrow) with ‘dirty’ shadowing.

26. Acute cholecystitis: MR
• Magnetic resonance imaging (MRI) may be useful for evaluating acute cholecystitis,
with a sensitivity (85%) and specificity (81%) similar to that of ultrasonography.
• MRI can be used in patients with equivocal ultrasonography findings or to visualize
hepatic and biliary abnormalities that cannot be characterized on ultrasonography.
* Kiewiet JJ, Leeuwenburgh MM, Bipat S, Bossuyt PM, Stoker J, Boermeester MA. A systematic review and meta-analysis of diagnostic
performance of imaging in acute cholecystitis. Radiology. 2012; 264(3):708-720.

27. Acute cholecystitis: Differentials
Liver abscess
Pyogenic liver abscesses may be idiopathic
or may result from seeding from infection
in the biliary tract, from the luminal
gastrointestinal tract or from the
portal/mesenteric venous system.
• USG: Round or oval hypoechoic mass
or masses, which may contain low-level
echoes.
• CT/MRI: Enhancing wall with
peripheral zone of edema
These findings are not universally present
Rupture of hepatocellular carcinoma
Spontaneous rupture of a hepatocellular
carcinoma with associated
hemoperitoneum is a frequent
complication in countries with a high
incidence of this tumor
Hepatocellular carcinoma usually is highly
vascular, and tumor necrosis with
associated hepatic capsular rupture and
rupture of vessels within the tumor is the
presumed etiology.
Differential diagnosis includes
spontaneous hemorrhage within a hepatic
adenoma or a hepatic metastasis

28. Hepatic abscess
Ultrasound (left image) shows a heterogeneously hypoechoic lesion corresponding to a hypodense lesion with
foci of gas on non-contrast CT (middle image). This lesion was heterogeneously T2 hyperintense on MRI (right
image) with enhancement and restricted diffusion (not shown).

29. Left upper quadrant

30. Splenic pathology
Splenic infarction
Splenic infarction may be focal and less
commonly global.
• Etiology:
 Secondary to bland or septic emboli to the
spleen
 Marked splenomegaly with outgrowth of the
splenic blood supply
 Pancreatitis
• Typical infarcts are wedge-shaped and
hypoattenuating on CT
Splenic abscess
Most splenic abscesses are secondary to
hematogenous dissemination of infection
and are seen primarily in
immunocompromised individuals and IV
drug abusers.
• On CT, splenic abscesses demonstrate
low attenuation centrally with an
enhancing rim and occasionally have
central gas.

31. Splenic abscess
73-year-old man with left upper
quadrant pain, fever, and
leukocytosis.
Transaxial contrast-enhanced CT
image shows a gas-containing
fluid collection in the spleen. A
drainage catheter was placed
percutaneously, and cultures grew
Escherichia coli

32. Splenic Arterial Infarcts
Arterial emboli commonly result in peripheral well-defined wedge-shaped lesions, as shown here on an
axial image (A). Coronal image (B) of the same CT showing the same infarct in the upper pole and another
smaller infarct in the lower pole. Multiple small hypodense lesions in this spleen represent micro-abscesses.
Emboli causing infarcts are therefore likely septic emboli.

33. Gastric pathology
The diagnosis of gastric pathology is best
established by endoscopy, although
patients may present with left or right
upper abdominal pain, and with other non-
specific signs and symptoms, and CT may
reveal the diagnosis when it is not clinically
suspected.
Acute gastric disorders include gastritis
and ulcer.
CT findings
• Focal or diffuse gastric wall
thickening,
• Increased mucosal enhancement
• Submucosal edema
• Peri-gastric inflammatory changes.
• Focal ulceration with or without
perforation (generally benign but
occasionally of malignant etiology)

34. Gastric ulcer
(A) Axial CT image showing benign ulcer (arrow) along the lesser curvature with a crater and surrounding
smooth mound. (B) Axial CT shows perforated gastric ulcer in the posterior gastric antrum with leaking contrast
(arrow), focal wall thickening and adjacent fat stranding.

35. Epigastric region

36. Acute pancreatitis
• Pancreatitis is inflammation of the pancreas, which may be due to a variety of
etiologies that share a final common pathway of premature activation of pancreatic
enzymes and resultant autodigestion of pancreatic parenchyma.
• On initial clinical evaluation, pancreatitis frequently is confused with other
disorders, and amylase and lipase levels may either be pending or not obtained.
Therefore it is important for the radiologist to identify pancreatitis, usually on CT
but occasionally on sonography, when the diagnosis is not suspected clinically.
• The vast majority of cases are due to gallstones or alcohol abuse. Less common
etiologies include trauma, interventional pancreatobiliary procedures, medications,
elevated triglycerides, congenital anomalies (i.e., pancreas divisum, annular
pancreas, absent dorsal pancreas), and underlying tumor.

37. Revised Atlanta
Classification
Revised Atlanta classification of acute
pancreatitis (2012) is an international
multidisciplinary classification of the
severity of acute pancreatitis, updating
the 1992 Atlanta classification.
It attempts to better characterize the
disease process, to standardize
terminology—including the
description of cross-sectional imaging
findings—and to provide better
correlation with prognosis.
Trikudanathan, G., Wolbrink, D., van Santvoort, H., Mallery, S., Freeman, M., & Besselink, M. (2019).
Current Concepts in Severe Acute and Necrotizing Pancreatitis: An Evidence-Based Approach.
Gastroenterology, 156(7), 1994-2007.e3. doi: 10.1053/j.gastro.2019.01.269

38. Modified CT severity index (CTSI)
Balthazar grade
Grade CT findings Score
A Normal CT 0
B Focal/diffuse pancreatic
enlargement
1
C Pancreatic gland abnormalities
and peri pancreatic
inflammation
2
D 1 Fluid collection 3
E ≥ 2 fluid collections and/or gas
bubbles in/adjacent to
pancreas
4
Pancreatic necrosis score
CT findings Score
No necrosis 0
< 30% necrosis 2
30-50% necrosis 4
> 50% necrosis 6
CT severity index (CTSI) combines the Balthazar grade (0-4 points) with the extent of
pancreatic necrosis (0-6 points) on a 10-point severity scale.

39. Modified CT severity index (CTSI)
DISEASE STRATIFICATION
• Mild (interstitial) pancreatitis : CTSI 0-2
• Balthazar B or C, without pancreatic or extra-pancreatic necrosis
• Intermediate (exudative) pancreatitis: CTSI 4-6
• Balthazar D or E, without pancreatic necrosis; peripancreatic collections are due to
extra-pancreatic necrosis
• Severe (necrotizing) pancreatitis: CTSI 8-10
• Necrosis of the pancreas (non-enhancing areas in the pancreas on contrast-enhanced
CT)

40. Acute pancreatitis
Contrast-enhanced axial CT (left image) demonstrates diffuse pancreatic enlargement and peripancreatic edema. The
pancreatic parenchyma enhances uniformly, without evidence for necrosis. Transverse ultrasound (right image) of
the head and body of the pancreas shows a diffusely enlarged, heterogeneous pancreas (arrows) due to pancreatic
edema.
Ultrasound case courtesy Julie Ritner, MD, Brigham and Women’s Hospital, Boston

41. Chronic pancreatitis
Two identical abdominal radiographs showing pancreatic calcification. There are
multiple irregular foci of calcification projected over the midline in the rough shape of
the pancreas. The right radiograph shows the pancreatic calcifications marked in
yellow

42. Right lower quadrant

43. ACR Appropriateness Criteria
Initial imaging of right lower quadrant (RLQ) pain
Expert Panel on Gastrointestinal Imaging, Kambadakone, A. R., Santillan, C. S., Kim, D. H., Fowler, K. J., Birkholz, J. H., Camacho, M. A., Cash, B. D., Dane,
B., Felker, R. A., Grossman, E. J., Korngold, E. K., Liu, P. S., Marin, D., McCrary, M., Pietryga, J. A., Weinstein, S., Zukotynski, K., & Carucci, L. R. (2022).
ACR Appropriateness Criteria® Right Lower Quadrant Pain: 2022 Update. Journal of the American College of Radiology : JACR, 19(11S), S445–S461.
https://doi.org/10.1016/j.jacr.2022.09.011

44. Acute appendicitis
• The starting symptom is generally nondescriptive visceral pain in the periumbilical
region, followed by nausea & vomiting. When the disease progresses, the pain
typically migrates to the right lower quadrant because of more localized peritoneal
inflammation.
• US performed as the initial diagnostic test, with CT performed only secondarily,
after US has yielded nondiagnostic findings.
• However, US can be limited by gas-filled bowel, which may obscure the underlying
abnormality and thus necessitate secondary CT in many individuals

45. Acute appendicitis
US remains the initial imaging examination,
despite its poor sensitivity and specificity
in this clinical setting.
In the evaluation of suspected appendicitis
in children (and in selected nonpregnant
women of childbearing age), US is
considered the initial examination of
choice, if available, although CT has a
higher accuracy.
Primary US criteria
• Swollen, non-compressible appendix
>7 mm in diameter (appendix can be
larger than 6 mm in transverse diameter
and can still be normal on CT),
• Target configuration
• Pain corresponding to the site of the
appendix.
• Other findings: Appendicolith or
multiple appendicolith

46. Acute appendicitis
(a–c) Ultrasonography of acute appendicitis in a 12-year-old girl. Oblique and transverse views show a
swollen appendix (diameter 10 mm), with a target configuration

47. Acute appendicitis: CT
Uncomplicated appendicitis
• Enlarged (> 6 mm) appendix (high
PPV)
• Adjacent fat infiltration (high
sensitivity)
• Visualization of appendicoliths (low
PPV because these may also be present in
individuals who do not have
appendicitis)
Perforated appendicitis
• Extraluminal gas, abscess
• Focal appendiceal wall defect
• Small-bowel obstruction (SBO)
* Daly CP, Cohan RH, Francis IR, Caoili EM, Ellis JH, Nan B. Incidence of acute appendicitis in patients with equivocal CT findings. AJR Am J Roentgenol
2005;184:1813–1820.
* Rao PM. Cecal apical changes with appendicitis: diagnosing appendicitis when the appendix is borderline abnormal or not seen. J Comput Assist Tomogr
1999;23: 55–59.
* Pereira JM, Sirlin CB, Pinto PS, Jeffrey RB, Stella DL, Casola G. Disproportionate fat stranding: a helpful CT sign in patients with acute abdominal pain.
RadioGraphics 2004;24:703–715.
* Bixby SD, Lucey BC, Soto JA, Theysohn JM, Ozonoff A, Varghese JC. Perforated versus nonperforated acute appendicitis: accuracy of multidetector CT
detection. Radiology 2006;241:780–786.
* Horrow MM, White DS, Horrow JC. Differentiation of perforated from nonperforated appendicitis at CT. Radiology 2003; 227:46–51.

48. Acute appendicitis
Axial CT image obtained after
intravenous administration of contrast
medium in 39- year-old woman with
classic clinical manifestations of
appendicitis shows retrocecal
inflamed appendix (arrow) with
thickened wall and some
surrounding infiltration.
The appendix could not be
visualized at US because of
overlying (bowel) gas. Appendicitis
was confirmed at surgery and
histopathologic analysis.
C: Cecum.

49. Acute appendicitis: MR
• Non-contrast MRI is being used increasingly in pregnant patients after
nondiagnostic US and has demonstrated high accuracy for diagnosis and exclusion
of appendicitis and for identification of alternative diagnoses.
• CT should be reserved as a third-line examination, used only if needed.

50. Acute appendicitis
Axial fat-saturated half-Fourier
acquisition with single-shot turbo
spin-echo MR image (1900/72
[repetition time msec/echo time
msec]) obtained in 28-year-old
woman who was at 18 weeks
gestation, was clinically suspected of
having appendicitis, and had
nondiagnostic US findings.
Image shows thickened retrocecal
appendix (arrow) with increased
signal intensity and minimal
infiltration of surrounding fat.
Fundus uteri is seen directly anterior
to the aorta. The diagnosis of
appendicitis was confirmed at surgery.

51. Acute appendicitis: Differentials
Common alternative conditions
• Crohn disease
• Right-sided colitis or diverticulitis
• Women: Pelvic inflammatory disease
(PID), ovarian cysts (and their
complications including rupture,
hemorrhage, and torsion)
Other alternative conditions
• Omental infarction (can present with
upper or mid right abdominal pain)
• Epiploic appendagitis
• Small bowel diverticulitis (ileal or
Meckel’s)

52. Ovarian torsion
Axial CT scan obtained after
intravenous contrast medium
administration in 24-year old woman
with right lower quadrant pain, a
clinical differential diagnosis of
gynecologic disorder (tubo-ovarian
abscess, pelvic inflammatory disease,
ovarian torsion) or appendicitis, and
inconclusive US findings shows a
normal appendix (straight arrow) and
an enlarged right ovary
(arrowheads), which most likely is
due to tubo-ovarian abscess or ovarian
torsion.
Free fluid and some thickening of
the peritoneum (curved arrows) are
also visible. Laparoscopy revealed
ovarian torsion.

53. Right-sided
diverticulitis
Axial CT images in 25-year-old
woman suspected of having
appendicitis.
At US, the appendix was not well
visualized; therefore, CT was
performed after intravenous contrast
medium administration. (a) Image
shows right-sided diverticulitis,
indicated by right-sided colon
diverticula (arrow) and fecalith
with thickened wall, wall
enhancement, and adjacent fat
infiltration (arrowheads). (b) Image
shows some secondary wall thickening
of the adjacent appendix (arrow), with
air in the lumen. Only some secondary
changes— and no appendicitis—are
seen.

54. Left lower quadrant
The ACR recommends CT as the initial imaging test for the evaluation of left
lower quadrant pain

55. ACR Appropriateness Criteria
Initial imaging of left lower quadrant (LLQ) pain
Expert Panel on Gastrointestinal Imaging:, Galgano, S. J., McNamara, M. M., Peterson, C. M., Kim, D. H., Fowler, K. J., Camacho, M. A., Cash, B. D., Chang,
K. J., Feig, B. W., Gage, K. L., Garcia, E. M., Kambadakone, A. R., Levy, A. D., Liu, P. S., Marin, D., Moreno, C., Pietryga, J. A., Smith, M. P., Weinstein, S., …
Carucci, L. R. (2019). ACR Appropriateness Criteria® Left Lower Quadrant Pain-Suspected Diverticulitis. Journal of the American College of
Radiology : JACR, 16(5S), S141–S149. https://doi.org/10.1016/j.jacr.2019.02.015

56. Acute colonic diverticulitis
• Diverticulitis is acute inflammation of an obstructed colonic diverticulum, leading
to diverticular wall ischemia and microperforation.
• Acute colonic diverticulitis is the second most common cause of acute abdominal
pain and the most common cause of left lower quadrant pain in adults.
• Diverticulitis is often diagnosed clinically without radiologic examination, but
imaging should be considered if the diagnosis is unclear or if complications (e.g.,
abscess, fistula, obstruction, perforation) are suspected.
• CT is the primary modality for diagnosis, triage, and evaluation of severity and
complications, according to guidelines of the American Society of Colorectal
Surgeons

57. Acute colonic diverticulitis: CT
Highly sensitive findings
• Wall thickening (95% sensitivity)
• Fat stranding (91% sensitivity)
Highly specific findings (but rare)
• Fascial thickening
• Inflamed diverticulum

58. Modified Hinchey Classification
Stage Characteristics
Uncomplicated diverticulitis
0 Mild clinical diverticulitis
1a Confined pericolic inflammation, no abscess
Complicated diverticulitis
1b Confined pericolic inflammation with local abscess
2 Pelvic, retroperitoneal, or distant intraperitoneal abscess
3 Generalized purulent peritonitis, no communication with bowel lumen
4 Feculent peritonitis, open communication with bowel lumen
Kaiser AM, Jiang JK, Lake JP, et al. The management of complicated diverticulitis and the role of computed tomography. Am J
Gastroenterol 2005;100:910–917.

59. Uncomplicated
diverticulitis
Axial CT shows fat stranding
surrounding a diverticulum at the
hepatic flexure (arrow).

60. Complicated
diverticulitis
Axial CT shows a large diverticulum
arising from the sigmoid colon
containing enteric contrast (yellow
arrow), with surrounding
mesenteric fat stranding. A few
adjacent locules of extraluminal gas
(red arrow) are present.

61. Acute colonic diverticulitis: Differential
Colorectal cancer
• Pericolonic lymph nodes
• Luminal mass
Diverticulitis
• Pericolonic inflammation
• Continuous (> 10 cm) segment
involvement
However, these signs are not very accurate, and cancer can be missed
Therefore, endoscopy and biopsy are often required to make this differentiation after
the clinical symptoms have resolved— often after 6 weeks.

62. Colorectal cancer
(a, b) Axial CT images obtained after
intravenous, oral, and rectal contrast
material administration in 46-year-
old man with 2-year history of
abdominal pain and recent
progressive acute abdominal pain.
He had not defecated for the past 2
days and had experienced weight loss
of 12 kg during the past year. Acute
diverticulitis was clinically suspected,
with colorectal cancer as a differential
diagnosis.
Images show (a) apple-core stenosis
(arrow) of the sigmoid colon caused by
colorectal cancer and (b) proximal
prestenotic dilatation of descending
colon and cecum (arrow).

63. Epiploic appendagitis
Epiploic appendagitis is a relatively
common, self-limiting condition, in which
an appendage of fat along the external
aspect of the colon, left side much more
common than right, undergoes torsion,
with subsequent venous thrombosis.
CT findings
• Swollen, ovoid, 1.5–3.5 cm fat-
containing focus with peripheral
thickening and associated
inflammation
• Adjacent colon is usually normal or
nearly normal.

64. Epiploic
appendagitis
Contrast-enhanced computed
tomography shows the inflamed
appendix epiploica as a fatty mass
with hyperattenuating rim adjacent
to the sigmoid colon (white arrow).
Note the central ‘vascular dot’ sign.

65. Left lower quadrant pain: Differentials
• Colitis
• Bowel ischemia
• Functional colonic disorders (especially constipation and also obstruction from a
variety of other etiologies)
• Urinary tract infection (UTI)
• Gynecologic disease

66. Pseudomembranous colitis
Axial (left image) and coronal (right image) contrast-enhanced CT demonstrates diffuse bowel wall
edema and mucosal enhancement of the entire colon (accordion sign) with pericolonic stranding
and mesenteric vasculature engorgement, consistent with pseudomembranous colitis in this patient
with fever, leukocytosis, and a positive C. diff. culture.

67. Acute non-localized pain
Differential diagnosis of acute nonlocalized abdominal pain is broad.
CT is typically the imaging modality of choice if there is significant concern
for serious pathology or if the diagnosis is unclear from history, physical
examination, and laboratory testing

68. ACR Appropriateness Criteria
Initial imaging of acute non-localized abdominal pain
Chang, K., Scheirey, C., Fowler, K., Therrien, J., Kim, D., WB, A.-R., Camacho, M., Cash, B., Garcia, E., Kambadakone, A., Lambert, D., Levy, A., Marin, D.,
Moreno, C., Noto, R., Peterson, C., Smith, M., Weinstein, S., &#38; Carucci, L. (2018). ACR Appropriateness Criteria Acute Nonlocalized Abdominal
Pain. Journal of the American College of Radiology https://doi.org/10.1016/j.jacr.2018.09.010

69. Diffuse abdominal pain: Common causes
Gastroenteritis
• CT findings often are normal
• Mild bowel wall thickening and
increased intraluminal fluid
Colitis
• Varying degrees of colonic wall
thickening/edema
• Inflammation of the adjacent fat
Any disorder that involves a large portion of the gastrointestinal tract or irritates the peritoneum
can cause diffuse abdominal pain. The most common disorder is gastroenteritis

70. Bowel obstruction
Bowel obstruction is a relatively frequent cause of acute abdominal pain.
The majority of patients found to have bowel obstruction after they present
to the ED have an small bowel obstruction (SBO).

71. Gastric obstruction
Abdominal radiograph showing a
gas‐filled dilated stomach.
There is a loop of stomach‐shaped
distended bowel in the upper
abdomen. On the right side of the
abdomen, you can see that the
duodenum is partially distended as
valvulae conniventes are seen.
The findings are suggestive of a
proximal small bowel obstruction,
possibly in the region of the distal
duodenum or proximal jejunum.

72. Small bowel obstruction (SBO)
Primary presentation
• Combination of vomiting, distended
abdomen, and increased bowel sounds is
suggestive of SBO
This has a positive predictive value of 64% *
Patient characteristics & risk factors
• Previous abdominal surgery
• Age older than 50 years
• History of constipation
* Bohner H, Yang Q, Franke C, Verreet PR, Ohmann C. Simple data from history and physical examination help to exclude bowel obstruction and to avoid
radiographic studies in patients with acute abdominal pain. Eur J Surg 1998;164:777–784.

73. Small bowel obstruction (SBO)
• For adequate treatment, it is important to identify the cause (eg, adhesion,
neoplasm, or hernia) and severity of the obstruction.
• An obstruction can be partial or complete and complicated by ischemia, especially
in the case of closed loop obstruction (strangulation).
• Radiography has long been the primary imaging modality of choice for patients
suspected of having bowel obstruction.
 * 69% sensitivity and 57% specificity
• CT has the best reported accuracy for the diagnosis of SBO
 * 94% sensitivity and 96% specificity
* Maglinte DD, Balthazar EJ, Kelvin FM, Megibow AJ. The role of radiology in the diagnosis of small-bowel obstruction. AJR Am J Roentgenol 1997;168:1171–
1180. 77.
* Megibow AJ. Bowel obstruction: evaluation with CT. Radiol Clin North Am 1994;32: 861–870.

74. Small bowel
obstruction (SBO)
Upright conventional abdominal
radiograph obtained in 59-year-old
man who had abdominal pain and a
distended abdomen at clinical
evaluation, as well as a history of SBO
3 years ago, for which he was treated
conservatively,
Radiography shows distended small-
bowel loops and air-fluid levels
(arrowheads), consistent with SBO.
The previous obstruction was most
likely caused by adhesions because the
patient had previously undergone
appendectomy. This patient was again
treated conservatively.

75. ACR Appropriateness Criteria: SBO
Complete or high-grade SBO
Abdominopelvic CT with intravenous
contrast medium
Low-grade or intermittent SBO
Several CT techniques appropriate:
• Abdominopelvic CT with barium or
water as the contrast agent, CT
enteroclysis
• Conventional: Follow-through,
conventional enteroclysis

76. Small bowel obstruction (SBO): CT
• Clear change in bowel diameter: Distended loops proximal to transition point &
collapsed loops distal to transition point
• Small-bowel feces sign (helpful sign for identifying the point of obstruction):
Feces-like material in the distended small bowel
• Transition point should be scrutinized for the cause of the obstruction adhesion,
neoplasm, hernia, or inflammatory disorder
• Because SBO is most often due to adhesions, which are usually not visible at CT, in
most patients, no cause will be identified at CT. In this setting, the diagnosis of SBO
due to adhesions is made by means of exclusion.

77. Small bowel
obstruction (SBO)
Sagittal reconstructed CT image in 47-
year-old woman who had a history of
lysis of adhesions and presented
with cramping pain of 2 days
duration, nausea, and vomiting
shows the transition point (arrow)
and the small-bowel feces sign
(arrowheads) proximal to the
transition point. No mass is visible,
and the diagnosis is obstruction by
adhesions. The patient was treated
conservatively with a successful
outcome.

78. Closed-loop small
bowel obstruction
62-year-old man with metastatic
colon cancer who presented with
severe abdominal pain, nausea, and
vomiting.
Transaxial contrast-enhanced CT
image shows a fluid-filled, distended
loop of small bowel in the left mid-
abdomen. Mesenteric edema and
mild wall thickening indicate bowel
ischemia. Note the two adjacent
collapsed segments of small bowel
(arrows), where the loop of small
bowel had entered an internal hernia

79. Small bowel obstruction (SBO): USG
US reportedly has good accuracy (81%) in the diagnosis of bowel obstruction *.
However the ACR states that US is the least appropriate imaging modality when high-
or low-grade SBO is suspected.
• Fluid-filled loops easily visualized
• Visualizing peristaltic movement: Differentiate between mechanical obstruction
and paralytic ileus
Gas-filled loops may obscure the underlying abnormality, which has important
treatment management–related implications. Obstruction is difficult to stage
accurately.
Overall, CT can be considered the primary imaging technique for patients suspected
of having SBO.
Schmutz GR, Benko A, Fournier L, Peron JM, Morel E, Chiche L. Small bowel obstruction: role and contribution of sonography. Eur Radiol
1997;7:1054–1058

80. Large bowel obstruction (LBO)
Common causes
• Colorectal cancer (60% cases)
• Sigmoid volvulus (10%–15% cases)
• Diverticulitis (10% cases)
Clinical features
• Abdominal pain
• Constipation
• Abdominal distention
These are not very specific and therefore,
clinical diagnosis is often incorrect.

81. Large bowel
obstruction (LBO): XR
Abdominal radiograph showing dilated
large bowel.
The large bowel is visible as there is
gas (black) within with a distension of
>5.5 cm, circumferential location and
visible haustra.

82. Large bowel obstruction (LBO): CT
• Traditionally, conventional radiography has been the initial imaging examination
performed.
• CT is the imaging modality of choice in the diagnosis of LBO. It can be used to
identify the cause of the obstruction, the level of obstruction, and the presence of a
complicated obstruction (eg, strangulation).
 96% sensitivity and 93% specificity
FINDINGS:
• Dilated colon (colon diameter > 5.5 cm, cecum diameter > 10 cm)
• Colon filled with feces, gas, and fluid proximal to an abrupt transition point, after
which the colon is collapsed distally
Frager D, Rovno HD, Baer JW, Bashist B, Friedman M. Prospective evaluation of colonic obstruction with computed tomography. Abdom
Imaging 1998;23:141–146.

83. Sigmoid volvulus
Abdominal radiograph showing a
sigmoid volvulus.
There is a ‘coffee bean’–shaped loop
of distended bowel crossing the
midline and extending to the right
upper quadrant. There is a general lack
of haustra. The proximal large bowel is
somewhat distended secondary to the
obstruction from the volvulus.

84. Cecal volvulus
Abdominal radiograph showing a
caecal volvulus.
There is a rounded comma‐shaped
loop of distended large bowel in the
centre of the abdomen with haustra
seen within. The remainder of the
colon distal to the caecal volvulus
(obstruction) is collapsed.

85. Cecal volvulus
Transverse CT image (a) and coronal
CT reformation (b) demonstrate a
markedly dilated cecum (C) located in
the midline and left lower abdomen
and upper pelvis. The arrow points to
the area of colonic twisting. Note the
dilated small bowel loops, due to the
proximal colonic obstruction

86. Perforated viscus
• Because the clinical symptoms of free perforation are associated with the
underlying cause of the perforation, the clinical presentations of patients with
perforated viscus are quite variable.
• Besides the variable symptoms of the underlying mechanism, a rigid abdomen
usually is present. Recognizing a perforation and establishing the cause and site of
the perforation can yield crucial information for the surgeon.

87. Perforated viscus
Common causes
• Perforated gastroduodenal peptic
ulcer
• Perforated diverticulitis
Uncommon causes
• Bowel carcinoma
• Infarction

88. Contained perforated diverticulitis
Axial CT images obtained in (a) abdominal and (b) lung window settings after intravenous contrast medium
administration in 71-year-old woman who had a 2-day history of left lower quadrant pain and was
suspected of having diverticulitis show diverticulitis of the sigmoid colon with a contained perforation
(arrow) and infiltration of pericolic fat. The patient was treated conservatively with antibiotics
Among patients who are evaluated for possible acute diverticulitis, only 1%–2% have
free perforation*
* Jacobs DO. Clinical practice: diverticulitis. N Engl J Med 2007;357:2057–2066.

89. Perforated duodenal ulcer
Axial CT images obtained after intravenous administration of contrast medium in 54-year-old woman who
presented to the ED with acute periumbilical abdominal pain that radiated to the back. The abdominal
pain started after the woman ingested a nonsteroidal anti-inflammatory drug. (a) Image obtained in lung
window setting shows free intraperitoneal air (arrow). (b) Image shows wall thickening at the duodenal
bulb and evidence of perforation (arrow), with adjacent soft-tissue infiltration and air bubbles
(arrowhead). A diagnosis of perforated duodenal ulcer was made and confirmed at surgery.

90. Bowel ischemia
Presentation
PRIMARY SYMPTOM:
• Short clinical history of prominent
abdominal pain
OTHER SYMPTOMS:
• Nausea & vomiting
• Diarrhea
• Distended abdomen
All of these symptoms are nonspecific.
A diagnosis of bowel ischemia is often made
after the more frequently occurring diagnoses
with similar associated symptoms are
excluded.
Risk factors
Bowel ischemia should be considered in the
following:
• Elderly patients with known
cardiovascular disease (eg, atrial
fibrillation)
• Younger patients with diseases that cause
inadequate mesenteric blood flow:
Vasculitis, hereditary or familial coagulation
disorders such as antiphospholipid
syndrome, and protein C or S deficiency.

91. Bowel ischemia: Biphasic CT
Arterial phase CT
• Evaluating the celiac trunk and the
mesenteric arteries
Venous phase CT
• Show occlusions of mesenteric arteries,
but it predominantly enables evaluation
of the mesenteric veins, bowel wall, and
other causes of acute abdominal pain

92. Bowel ischemia: CT
Specific CT findings
• Clear sign of mesenteric ischemia:
Occluded mesenteric arteries or venous
thrombus
• Thickened bowel wall (> 3 mm): Because
of mural edema, hemorrhage, congestion, or
superinfection. Thickening owing to edema,
congestion, or hemorrhage is a frequent
finding of venous obstruction.
• Bowel wall hypoattenuation (edema)
• Bowel wall hyperattenuation
(hemorrhage)
• Target sign: Abnormal bowel wall
enhancement
• Absence of bowel wall enhancement
(highly specific but often missed)
Other findings
• Impending perforation: Paper-thin bowel
wall
• Irreversible ischemia: Luminal dilatation
and fluid levels (fluid exudation of the
ischemic bowel segments)

93. Bowel ischemia
Multiplanar reformatted abdominal CT
images obtained in (a) soft-tissue and (b)
lung windows after intravenous
administration of contrast material in 59-
year-old woman with nausea and
vomiting who had undergone sigmoid
colon resection for a gastrointestinal
stromal tumor 5 days earlier. A
distended abdomen identified at physical
examination and an increasing C-reactive
protein level were noted.
Images show portovenous gas (straight
arrows) in the periphery of the liver and
pneumatosis (curved arrows). The bowel
wall (arrowheads) is thickened and
enhanced. On the basis of these CT
findings, bowel ischemia was considered.
However, the clinical findings were more
suggestive of bacterial translocation. The
patient responded well to treatment with
antibiotics.
Images courtesy of Ludo F.M. Beenen, MD, Academisch Medisch Centrum, Universiteit van
Amsterdam, Amsterdam, the Netherlands

94. Bowel ischemia
secondary to SMA
thrombosis
52-year-old man with 4-day history
of severe diffuse abdominal pain.
Transaxial (a, b) and sagittal curved
planar reformatted (c) contrast-
enhanced CT images demonstrate
thrombosis of the superior
mesenteric artery (large white
arrow). Note the bowel pneumatosis
(small black arrow) and gas within the
mesenteric veins (small white arrow)
indicative of bowel ischemia

95. Conclusion
The clinical findings–based diagnosis rendered in patients with acute abdominal pain
is often inaccurate. Therefore, imaging plays an important role in the treatment of
patients with acute abdominal pain.
Because US and CT are widely available, radiography is rarely indicated for the
examination of patients with acute abdominal pain, with the exception of select
patients groups

96. Reference
Books
• Adam, A., Dixon, A. K., Gillard, J. H., &
Schaefer-Prokop, C. M. (2021). Grainger &
Allison’s Diagnostic Radiology: A textbook
of medical imaging. Elsevier.
• Diseases of the Abdomen and Pelvis
2018-2021. (2018). IDKD Springer Series.
doi: 10.1007/978-3-319-75019-4
• Mandell, J. (2013). Core Radiology: A
Visual Approach to Diagnostic Imaging.
Cambridge: Cambridge University Press.
doi:10.1017/CBO9781139225762
Journals
• Stoker, J., van Randen, A., Laméris, W., &
Boermeester, M. A. (2009). Imaging
Patients with Acute Abdominal Pain.
Radiology, 253(1), 31-46.
https://doi.org/10.1148/radiol.25310903
02
• Cartwright, S. L., & Knudson, M. P. (2015).
Diagnostic imaging of acute abdominal
pain in adults. American family physician,
91(7), 452–459.

97. Thank you