Ultrasound is useful for evaluating the kidneys. It can identify normal anatomy as well as congenital anomalies, masses, cysts, infections, kidney stones and other pathologies. For kidney masses, ultrasound can determine if they are solid or cystic. Specific pathologies like renal cell carcinoma, angiomyolipoma and polycystic kidney disease have characteristic ultrasound features that help in diagnosis. Ultrasound is also used to evaluate hydronephrosis and guide interventional procedures.

1. Ultrasound of Kidneys
PRESENTER: DR. AMIT GAUTAM
1ST YEAR RESIDENT,
DEPARTMENT OF RADIOLOGY, CMCTH(TU)

2. OBJECTIVES
ANATOMY OF KIDNEYS
NORMAL ANATOMICAL VARIANTS AND CONGENITAL ANOMALIES
DISEASE OF RENAL PARENCHYMA AND ITS SONOGRAPHIC FINDINGS

3. EMBRYOLOGY

4. ANATOMY
 Adult kidney: 9-13 cm long, 2.5 cm thick and 5 cm wide (approximately)
 Right kidney smaller than left kidney ( but not more than 1.5 cm).
 Left kidney 1.2 cm higher than right kidney.
 Borders
lateral- convex
medial-concave with hilum

5. Internal Structure of Kidney

6. Sonographic Technique
Should be assessed in both sagittal and transverse plane.

7. Contd…

8. Normal Anatomical Variation
1. Persistent fetal lobulations
◦ due to incomplete fusion of developing renal lobules
◦ seen as smooth indentations of renal outline

9. Contd..
2. Junctional Parenchymal defect
due to incomplete fusion of renal lobes
located between upper and mid poles of the kidney
typically triangular in shape.

10. Contd..
3. Hypertrophied column of Bertin
◦ Columns of Bertin : extension of renal cortical tissue which separates the pyramids
◦ They become of radiologic importance when they are unusually enlarged and may
be mistaken for a renal mass.

12. Contd..
4. Extrarenal Pelvis
Renal pelvis is outside the confinement of hilum
More distensile than the intrarenal pelvis thus
may be confused for proximal hydroureter.

13. 5. Dromadary hump
Prominent superolateral border of the left kidney
due to impression of spleen or fetal lobulation.
It may be mistaken for a renal mass.

14. Congenital Anomalies of Kidney
1. Anomalies related to renal growth
a. Hypoplasia: too few nephrons. Unilateral Vs. Bilateral.
US findings: kidney is small but otherwise normal
b. Compensatory hypertrophy:
Diffuse Vs. Focal

15. Contd..
2. Anomalies related to ascent of kidney
a. Ectopia: failure to ascend during embryonic development.

16. B. Crossed renal ectopia:
both kidneys are on same side and typically fused ( Crossed-fused ectopia)

17. C. Horse-shoe Kidney:
Occurs when metanephric blastema fuse prior to ascent.
Sonographic findings:
isthmus crossing the midline anterior to the great vessels.

18. Abnormal rotation of pelves
PUJ obstruction
Infection and stone formation
Associated Anomalies: VUR, duplex collecting system, retrocaval ureter, anorectal
malformation, rectovaginal fistula, omphalocele, etc.

19. 3. Anomalies related to ascent of kidney
a. Renal agenesis
Unilateral Vs. Bilateral
Occurs due to:
Absence of metanephric blastema
Absence of ureteric bud development
Absence of interaction of ureteric bud with metanephric blastema

20. Sonographic finding
Although kidney is absent, adrenal gland is usually present ( absent in upto 17%
patient )
Compensatory hypertrophy of another kidney
Usually colon falls into empty renal bed.
Associated anomalies: anorectal malformation and crptoorchidism

21. b. Supernumerary kidney:

22. c. Duplex collecting system
A congenital abnormality where drainage of the kidney is
via two collecting systems (occurring in 10% of individuals)
May be complete or incomplete (incomplete > complete)

23. WEIGERT-MEYER RULE

24. Contd..

25. HYDRONEPHROSIS
Refers to dilatation of the collecting system.
Sonographic evaluation should include assessment of the degree of dilatation,
appearance of surrounding parenchyma, level of obstruction and any
obstructing lesion.
Hydronephrosis that persists after voiding suggests an anatomic obstruction.

26. Grading of Hydronephrosis

27. Hydronephrosis Vs. Parapelvic Cysts

28. Pyelonephritis
1. Acute Pyelonephritis
Tubulointerstitial inflammation of kidney.
Ascending Vs. Hematogenous seeding.
In most cases, sonography is normal .

30. 2. Renal and perinephric abscess:
Complication of acute pyelonephritis leading to parenchymal necrosis and abscess formation.
Renal abscess tends to be solitary and may spontaneously decompress into the collecting
system or perinephric space.
SONOGRAPHIC FINDINGS
Renal abscesses appear as round thick-walled hypoechoic complex
Internal mobile debris and septation may be seen
Occasionally dirty shadowing may be seen posterior to gas within abscess.
D/D: hemorrhagic or infected cyst, parasitic cyst, multiloculated cysts and cystic neoplasms.

32. 3. Emphysematous Pyelonephritis
Uncommon life-threatening infection of renal parenchyma characterize by gas
formation
Two types of disease: EPN 1 and EPN 2
EPN 1: Parenchymal destruction and mottled gas.
EPN 2: Renal or perirenal fluid collections with loculated gas in the collecting
system

34. 4. Chronic Pyelonephritis
Interstitial nephritis often associated with VUR.
Sonographic findings:
Dilated blunt calix is seen, associated with cortical scar or atrophy.

36. 5. Xanthogranulomatous Pyelonephritis
Chronic suppurative renal infection in which destroyed renal parenchyma is replaced by lipid-
laden macrophages.
Typically unilateral
Diffuse ,focal or segmental
Associated with nephrolithiasis and obstructive nephropathy.

37. Sonographic finding
Renal enlargement.
Maintenance of reniform shape
 Loss of CMD

38. Pyonephrosis
Purulent material in an obstructed collecting system.
Sonography: layering collecting system echoes

39. Papillary Necrosis
Etiology: Analgesic abuse, diabetes, UTI, renal vein thrombosis, prolonged
hypotension, dehydration, urinary tract obstruction,hemophila
Initially papilla swells, then a communication with the caliceal system occurs
The central area of papilla slough and cavitates.

41. Renal Tuberculosis
Hematogenous seeding of the kidney from an extra urinary source typically
lungs
Typically unilateral.
SONOGRAPHIC FINDINGS
Early changes includes development of multiple small bilateral tuberculoma
Most frequently encountered abnormality was focal renal lesions
Papillary involvement is noted when sonolucent linear tract is shown extending
from the involved calix into the papilla.

42. Chronic form of genitourinary tract TB : fibrotic, strictures, extensive cavitation, calcification,
mass lesions, perinephric abscess and fistula.
With time calcification in the areas of caseation or sloughed papilla may occur
If renal infection ruptures perirenal abscess is formed.
The hallmark of chronic renal TB is a small, non functional calcified kidney called PUTTY kidney

43. Fig A. caseous cavity
Fig B.Tuberculous cavity
with fine septae within
Fig c. Irregular
hypoechoic cavities
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44. Renal Hydatid Disease
Usually solitary and typically involves the renal poles.
Suggestive featues: including floating membranes, daughter cysts, and thick, double-contour
cyst walls.

45. D. ACQUIRED IMMUNODEFICIENCY SYNDROME.
SONOGRAPHIC FINDINGS
Greatly increased renal echogenicity
Globular appearing kidney
Decreased corticomedullary differentiation
Decrease renal sinus fat and heterogeneity
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46. RENAL CALCULI
 60-80 % composed of calcium.
Predisposing factors : dehydration, urinary stasis, hyperuricemia, hyperparathyroidism and
hypercalciuria.
Caliceal calculi that are non-obstructing are usually asymptomatic.
Obstruction at three areas of ureteric narrowing a) just past the PUJ b) where the ureter
crosses the iliac vessels and c) VUJ
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47. Sonographic finding

49. F. NEPHROCALCINOSIS:
Renal parenchymal calcification
Two types dystrophic and metastatic.
DYSTROPHIC: deposition of calcium in ischemic or necrotic tissue
occurs in tumors, abscess and hematomas.
METASTATIC: Due to hypercalcemic state caused by hyperparathyroidism, renal
tubular acidosis and renal failure.
Metastatic calcification have 2 types: cortical (5%) and medullary (95%)
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50. NEPHROCALCINOSISCONT…..
CORTICAL NEPHROCALCINOSIS CAUSE:
Acute cortical nephrosis
Chronic glomerulonephritis
Hypercalcemia
Ethylene glycol poisoning
Sickle cell anemia
Renal transplant rejection
MEDULLARY NEPHROCALCINOSIS CAUSE
• Hyperparathyroidism
• Renal tubular acidosis
• Medullary spongy kidney
• Bone metastases
• Chronic pyelonephritis
• Cushing syndrome
• Hyperthyroidism
• Malignancy
• Renal papillary necrosis
• Sarcoidosis
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51. Sonographic findings
Early medullary calcification are non shadowing echogenic rims surrounding medullary
pyramids.
Further calcium deposition results in acoustic shadowing.
Early cortical calcification may be suggested by increased cortical echogenicity.
 With progressive calcification, a continuous,shadowing calcified rim develops.

52. NEPHROCALCINOSISCONT……
SONOGRAPHIC FINDINGS:
Early medullary calcification are non shadowing echogenic rims surrounding medullary pyramids.
Further calcium deposition results in acoustic shadowing
Early cortical calcification may be suggested by increase cortical echogenicity.
With progressive calcification, a continuous, shadowing calcified rim develops.
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53. Renal Cell Carcinoma
Accounts for approximately 3% of all adult malignancy and 86% of all primary malignant renal
parenchymal tumors.
Histological subtypes include:
a) Clear cell ( 70% – 75%)
b) Papillary (15%)
c) Chromophobe(5%)
d) Oncocytic(2% -3%)
e) Collecting duct or medullary(<1%)

54. Sonographic findings
May be hypoechoic, hyperechoic or isoechoic.
RCCs less than 3cm are mostly echogenic.
A small Echogenic RCC may be difficult to differentiate from a benign angiomyolipoma at
ultrasound.
5-7 % of all RCCs are cystic.

57. Robson Staging Classification for RCC
STAGE I : Tumor confined within renal capsule
STAGE II : Invasive of perinephric fat
STAGE III: Involves lymph nodes or vascular structures
STAGE IV: Invasion of adjacent organs or distant metastasis

58. Transitional Cell Carcinoma
TCC of renal pelvis accounts for 7% of all primary renal tumors.
 > 65 years old.
SONOGRAPHIC FINDINGS
Morphology of lesions a) papillary b) non-papillary c) infiltrative
Small non obstructing tumors may be impossible to visualize in ultrasound.
With growth, papillary tumors will be seen as discrete, solid, central, hypoechoic renal sinus
masses with or without associated proximal caliectasis .
D/Ds: Blood clots, Sloughed, papillae and fungus balls.

60. Squamous Cell Carcinoma
Chronic infection, irritation, and stones lead to squamous metaplasia and
leukoplakia of the urothelium.
As with other infiltrating renal lesions, renal SCC appears at sonography as a
diffusely enlarged kidney that has maintained its reniform shape.
Normal renal echotexture is damaged and renal stone may be presented .

61. Adenocarcinoma
Almost all patients with adenocarcinoma of the renal pelvis have a
history of chronic UTI
Two-thirds have a stone, typically a staghorn calculus.

62. Oncocytoma
There is no distinctive ultrasound appearance of oncocytomas
Lesions may be homogenous or heterogenous with a distinct or poorly
demarcated wall
Central scar, calcification may be seen
Lack of specificity of imaging features of oncocytomas typically prompts
surgical resection

63. Angiomyolipoma
Benign renal tumors composed of varying proportions of adipose tissue,
smooth muscle cells, and blood vessels
Up to 50% of patients with AMLs will have clinical stigmata of tuberous
sclerosis (mental retardation, epilepsy, facial sebaceous adenomas)

64. Sonographic findings
the echo pattern of AMLs depends on the proportions of fat, smooth muscle, vascular elements,
and hemorrhage
If muscle, hemorrhage, or vascular elements predominate hypoechoic
Multiple fat and non fat interfaces in the more typical echogenic lesion with shadowing

65. Lymphoma
Lymphomatous involvement of the kidney occurs either from hematogenous dissemination or
contiguous extension of retroperitoneal disease.
 Bilateral > Unilateral
Sonography:
 depends on the pattern of involvement
 Focal parenchymal involvement may appear as solitary or multiple nodules. These masses
appear homogeneous and hypoechoic or anechoic.
Solitary: Focal hypoechoic mass indistinct from renal cell carcinoma
Multiple: Usually bilateral, hypoechoic renal mass.

66. Metastases to Kidney
Hematogenous route.
The most common primary tumors giving rise to renal metastases :
(1) Lung carcinoma,
(2) Breast carcinoma, and
(3) RCC of the contralateral kidney
May manifest as a solitary mass, multiple masses, or a diffusely infiltrating
mass that enlarges the kidney.

67. SONOGRAPHIC FINDING:
 A solitary metastasis : solid mass indistinguishable from RCC; often occurs with
colon carcinoma.
 Multiple metastases : small, poorly marginated, hypoechoic masses.
Involvement of the perinephric space is possible, particularly with malignant
melanoma and lung cancer.
 infiltrating renal metastases are particularly subtle at ultrasound; as with other
infiltrating processes, the only manifestation at sonography may be an enlarged,
but still reniform, kidney.

68. Renal Cystic Disease
Cortical Cysts
1. Simple Cysts
 Benign and fluid filled
Likely originated from distal or collecting ducts
Most cysts are asymptomatic while large cysts may present with flank pain and hematuria.
A cyst is confidently characterized at sonography when it is:
(1) anechoic
(2) Has a sharply defined, imperceptible back wall
(3) Is round or ovoid
(4) Enhances sound transmission
If all these criteria are met further follow up is not required.

70. 2. Complex Cysts
 containing internal echoes, septations, calcifications, perceptible defined walls
and mural nodularity.

71. 71

72. Medullary Cysts
1. Medullary Sponge Disease
dilated and ectatic collecting tubules
2. Medullary Cystic Disease
Characterized by small cysts at the corticomedullary junction and medulla.
Tubulointerstial fibrosis is a hallmark of both entities.
At sonography small echogenic kidneys with medullary cysts 0.1 to 1.0 cm are
seen.

73. Polycystic Kidney Disease
AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE (ARPKD)
four types—perinatal, neonatal, infantile, and juvenile
characterized pathologically as a spectrum of dilated renal collecting tubules,
hepatic cysts, and periportal fibrosis .
SONOGRAPHIC FINDING:
 lack of corticomedullary differentiation and massively enla.rged echogenic kidneys

75. AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE:
Bilateral large cortical and medullary cysts
Associated anomalies :liver cysts (30%-60%); pancreatic cysts (10%); splenic cysts (5%)
Sonography finding:
Kidneys are enlarged and replaced by multiple bilateral, asymmetric cysts of varying size
Cysts complicated by hemorrhage or infection have thick walls, internal echoes, and/ or fluid-
debris levels
Dystrophic calcification within cyst walls or stones may be seen as echogenic foci with sharp,
distal acoustic shadowing.

77. Multicystic dysplastic kidney
 nonhereditary developmental anomaly also known as renal dysplasia, renal dysgenesis, and
multicystic kidney.
Sonography finding:
(1) Multiple noncommunicating cysts of varying size,
(2) Absence of normal parenchyma and normal
renal sinus, and
(3) Focal echogenic areas representing primitive
mesenchyme or tiny cysts

78. Renal Injuries
May be blunt or penetrating
Classified into four category:
I) Minor Injury: Contusions, subcapsular hematoma, small cortical infract
and lacerations that do not extend into the collecting system
II) Major Injury: Renal lacerations that extends into the renal collecting system
and segmental renal infract
III) Catastrophic Injury: Vascular pedicle injury and shattered kidney
IV) Uteropelvic Junction Avulsion

80. Sonographic findings
Renal hematomas : hypoechoic, hyperechoic, or heterogeneous
Lacerations : linear defects
Associated perirenal collections
Subcapsular hemorrhage

81. Medical Genitourinary Diseases
1. ACUTE TUBULAR NECROSIS (ATN):
Related to deposition of cellular debris within the renal collecting tubules
Sonographic appearance depends on the underlying cause
ATN caused by hypotension : kidneys may appear normal
Drugs, metals, and solvents : enlarged, echogenic kidneys

82. 2. Glomerulonephritis
Necrosis and mesangial proliferation of the glomerulus are the hallmarks of acute
glomerulonephritis.
The echo pattern of the cortex is altered; renal cortex may be normal, echogenic, or
hypoechoic, but the medulla is spared
Chronic glomerulonephritis
Profound, global, symmetrical parenchymal loss occurs.
The calices and papillae are normal, and the amount of peripelvic fat increases

83. 3. ACUTE INTERSTITIAL NEPHRITIS :
 Acute interstitial nephritis is an acute hypersensitivity reaction of the kidney most often
related to drugs
 At sonography, enlarged echogenic kidneys are noted
DIABETES
 At sonography, the kidneys are initially enlarged but, with time and progressive renal insufficiency, the kidneys
decrease in size and increase in cortical echogenicity .
 Corticomedullary junctions are preserved.
 With end-stage disease, the kidneys become smaller and more echogenic, and the medulla becomes as
echogenic as the cortex
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