This document provides information on performing and interpreting a renal ultrasound exam. It discusses the normal anatomy of the kidneys and collecting system. Common clinical indications for renal ultrasound include suspected renal colic and evaluation for hydronephrosis. The protocol for the exam and approaches for scanning each kidney are outlined. Normal variants, grades of hydronephrosis, stones, cysts, masses and other pathologies are described along with their ultrasound appearances. Pitfalls in the exam are also noted.

1. Doaa Sharaf.MD

2. Why?
 “Bones can break, muscles can atrophy,
glands can loaf about and even the brain can
sleep without immediate danger to survival.
BUT when the kidneys fail…. Neither bone,
muscle, gland nor brain could carry on.”
Homer William Smith,
“The Evolution of the Kidney”, (1943).

3. Objectives
Clinical indications for performing renal US
Approach to performing the US study
Normal anatomy.
Normal variant.
Abnormal findings
Clinical Impact

4. Protocol
•Both Kidneys
•Urinary Bladder
•+/- Residual Volume
•Aorta.
•Local protocol if needed.
•Full bladder

5. Clinical Indications for Renal
Ultrasound
Suspected renal colic
 Colicky flank pain radiating to groin
 Hematuria.
 During routine investigations for other systems.
Clinical question:
 Presence of hydronephrosis
 Absence of other pathology

6. Performing the Study
Patient preparation:
 None.
Transducer: 3.0MHz or 3.5 MHz
 5.0 MHz for thin patient.
Patient positioning
 Supine
 Posterior oblique, lateral decubitus, prone

7. Anatomy
Kidneys are retroperitoneal, T12 - L4
Right kidney is lower than the left kidney
Right kidney is posterio-inferior to liver &
gallbladder
Left kidney is inferior-medial to the spleen.
Arterial supply: renal artery from aorta.
Venous drainage: renal vein drain into IVC.
Adrenal glands are superior, anterior, medial to each
kidney

8. IVC
AORTA
Celiac
axis
SMA
Renal artery
Renal vein
Hepatic
Veins
Right
kidney
Left
kidney
Liver
Spleen

9. Renal Scanning Approaches

10. Approach to Scanning
 Right kidney scanning
approach: anterior, lateral,
posterior.
 Liver is the acoustic window
 Left kidney: requires a posterior
approach, through the spleen
(acoustic shadow)
 Air-filled bowel impedes
anterior scanning
I
LIVER STOMACH
SPLEEN
IVC
AORTAK K
S

11. Right Kidney Long Axis (LS)
Right lower ICS in
the MAL.

12. Liver
Diaphragm
Sinus
Cortex
Anterior
Posterior
Superior Inferior
Right Kidney Long Axis

13. Right Kidney Short Axis (TS)

14. Right Kidney Short Axis (TS)
Vertebral
Body
R Kidney
Aorta
Renal a.
GB
IVC
Liver
Anterior
Posterior
Right Left

15. Left Kidney Long Axis (LS)
Posterior axillary line

16. Left Kidney Long Axis
Anterior
Posterior
Superior Inferior
Spleen
Kidney
Rib
Shadow

17. Left Kidney Short Axis
Lower intercostal space

18. Left Kidney Short Axis
Anterior
Posterior
Right LeftLiver
Spleen
L Kidney

19. 9-12 cm length, 4-5 cm width, 3-4 cm thickness.
Gerota’s fascia encloses kidney, capsule, perinephric
fat Sinus:
 Hilum: vessels, nerves, lymphatics, ureter
 Pelvis: major and minor calyces.
Parenchyma surrounds the sinus
 Cortex: site of urine formation, contains nephrons
 Medulla: contains pyramids that pass urine to minor calyces.
Columns of Bertin separate pyramids
Anatomy

20. Renal artery
Renal vein
UreterRenal capsule
Cortex
Medullary pyramids
Minor
Calyx
Kidney Anatomy
Medulla
Sinus
Major
Calyx

21. Sonographic Appearance
Capsule is smooth and echogenic
Cortex is mid-gray, less echogenic than liver or
spleen.
Medullary pyramids are hypoechoic
 Renal sinus is echogenic due to fat
 Renal pelvis is black when visible.
The main artery: triphasic wave
The main renal vein is monophasic

23. Main renal artery at the hilum of the kidney is of
sharp systole, low resistance with good end-diastolic
flow. The spectrum from the adjacent vein can be
seen below the baseline.

24. Sonographic Appearance
Ureters are normally not seen.
When the bladder is distended with urine, the
walls are thin, regular and hyperechoic.
Bladder volume calculated according to the
formula:
Bladder volume (ml) = length x width x APD (cm) x 0.56
The ureteric orifices can be demonstrated in a
transverse section at the bladder base. Ureteric
jets can easily be demonstrated (N: 1.5 up to 12.4
times per minute)

26. Common Pitfalls in Renal Scanning
Failure to scan both kidneys.
Mistaking prominent renal pyramids for
hydronephrosis.
Mistaking prominent pyramids for cysts.
Confusing normal renal arteries for the
ureter.

27. Common Pitfalls in Renal Scanning
Failure to scan through the bladder to
search for stone at the uretero-vesicular
junction.
Inability to visualize left kidney due to
anterior probe placement.
Failure to scan the aorta in suspected renal
colic

28. Persistent fetal lobulations:
 Indentations on the surface of the kidney forming fetal
lobulations which may persist into adulthood.
Dromedary humps:
 Lateral kidney bulge, same echogenicity as the cortex.
Hypertrophied column of Bertin:
 Cortical tissue indents the renal sinus.
Hilar lips:
 Cortical tissue indents the renal sinus
Normal Variants

29. Normal Variants

31. Normal Variants
Renal agenesis:
 Failure of ureteric bud to reach metanephros.
 Occurs with VACTERL syndrome:
- Vertebral
- Anorectal.
- C.V.S.
- Tracheal.
- Eosophageal.
- Renal.
- Limb malformations.

32. Normal Variants
Double collecting system:
 Two separate collecting
systems and duplex ureters ;
complete or incomplete.
 Upper moeity mostly with
ureterocele.
 Lower moeity mostly with
reflux.

33. Normal Variants
 Horseshoe kidney:
 Kidneys are connected,
usually at the lower pole
 Renal ectopia:
 One or both kidneys
outside the normal renal
fossa.
 Crossed fused
kidney:
 One or both kidneys
outside the normal renal
fossa

36. Extra renal pelvis
The renal pelvis projects outside
the kidney, medial to the renal
sinus.
This is best seen in a transverse
section through the renal hilum.
It is important to distinguish it
from dilated PCS, parapelvic cyst
or collection.

37. Pelviureteral junction obstruction
Defined as obstruction of outflow
of urine from renal pelvis to
proximal ureter.
May be due to intrinsic, extrinsic
cause or crossing vessels.
Should do diuretic renography to
assess renal function

38. Hydronephrosis
Dilatation of the collecting system
proximal to the site of obstruction.

39. Hydronephrosis
Intrinsic, acquired
 Renal lithiasis
 Neoplasm (renal, ureteral, bladder)
 Papillary necrosis
 Ureterocele
 Blood clot
 Neurogenic bladder
 Anticholinergics
 Pregnancy, PID, uterine prolapse)
 Diuretics
 Vesico-ureteral reflux
 Diabetes insipidus
Intrinsic, congenital
 Stenosis (ureteral,
urethral, meatal)
 Adynamic ureter
 Spinal cord defects
 Duplication of the ureter
 Ureterocele

41. Grades of hydronephrosis
Mild
 Minimal separation of calyces
Moderate
 Dilation of major and minor
calyceal system
Severe
 Marked dilation of the renal
pelvis and thinning of the renal
parenchyma

42. Grades of Hydronephrosis

43. Stones
 Renal calculi are a common finding on ultrasound.
 May be asypmtomatic or cause of haematuria.
 The common types include:
● Calcium stones: most common in patients who have
abnormal calcium metabolism.
● Struvite (triple phosphate) stones: large, staghorn calculi
in patients with UTI.
● Uric acid stones: rare in patients with gout.
● Cystine stones: the rarest of all and result from a disorder
of amino acid metabolism—cystinuria.

44. Stones
 Hyperechoic.
 Distal shadowing.
 If fills the whole P.C.S. called stag horn stone.

45. Stag Horn Stone

46. Nephrocalcinosis
 Deposition of calcium in the renal
parenchyma.
 Related to the medullary pyramids and is
frequently associated with medullary
sponge kidney.
 In patients with disorders of calcium
metabolism,e.g. hyperparathyroidism.
 Regular arrangement of hyperechoic
pyramids are seen, numerous and tiny, as
they are smaller than the beam width.

47. Renal Masses
Ultrasound visualizes renal masses
Masses may be cystic or solid.
A) Cystic masses may
 Simple cysts.
 Complex cysts Bosniak classification.
 Infective: Hydatid cyst.
B) Masses
 Inflammatory:-Abscess.
-Xanthogranulomatous pyelonephritis.
 Neoplastic: -Benign
-Malignant.

48. Simple Renal Cysts
The most common renal mass is a simple cyst up to 50% of
the population, the incidence increasing with age.
A parapelvic cyst may be difficult to distinguish from
pelvicalyceal dilatation or an extrarenal pelvis, it cause
filling defect on intravenous urogram (IVU)
Cysts can hemorrhage causing pain.
Large cysts, particularly of the lower pole, may be palpable.

49. Renal Cysts
Renal cysts display three basic characteristics:
- Anechoic.
- Thin, well-defined capsule.
- Exhibit posterior enhancement.
Haemorrhage or infection can give rise to low-level echoes
within a cyst.
The capsule may display calcification.

50. Ultrasound Appearance

51. Problems & Pitfalls
Mistaking cysts for hydronephrosis
Mistaking cysts for aortic aneurysm

52. Characters of Renal Cysts
Commonly single rather than multiple
Cysts do not communicate; hydronephrosis
does
Shape is round or oval
Echo free
Sharp interface between the mass and renal
tissue
Large renal cysts may be mistaken for aortic
aneurysms

53. Autosomal Dominant (adult)
Polycystic Kidney Disease (APKD)
This is autosomal dominant AD
disease
It is normally associated with
progressive renal failure.
In about 50% of cases, cysts are
present in the liver, spleen and
pancreas, ovarian and arachnoids
cysts.

54. Ultrasound Appearance
There is often little or no
demonstrable normal renal
tissue.
Some are simple, other are
hemorrhagic and may contain
stones inside.
Bilateral enlarged kidneys with multiple cysts of various
sizes, not connected to each other or to renal pelvis, and
many having irregular margins

55. Multicystic Dysplastic Kidney
(MCDK)
This is a congenital malformation of
the kidney, in which the renal tissue is
completely replaced by cysts.
Mostly unilateral, diagnosed
prenatally (lethal if bilateral).
• Occurs as a result of severe early renal obstruction during
development in utero. Obstructed calyces become blocked off,
forming numerous cysts which do not connect.

56. Complex Renal Cysts

57. Complex Renal Cysts

58. Hydatid Cyst
The Echinococcus parasite.
The parasite forms a cyst
which has a thickened wall,
often with smaller, peripheral
daughter cysts. Frequently the
main cyst contains echoes.
May contain floating
membrane indicating
impending rupture

59. Renal pathology
B: Renal Mass
1- Inflammatory
-Renal Abcess
-Xanthogranulomatous pyelonephritis
2- Neoplastic
-Benign
-Malignant

60. Renal Abscess
A renal abscess is generally a progression
of focal inflammation within the kidney
Complex mass with distal acoustic
enhancement.
-ill-defined margins at first then become
more obvious.
-increased echogenicity due to low-level
echoes from pus, but it may also be
hypoechoic.
-Non liquefied center
The abscess may be intrarenal,
subcapsular or perirenal.

61. Xanthogranulomatous pyelonephritis
(XGP)
Classic triad of
xanthogranulomatous
pyelonephritis:
(Bear Paw Sign)
- Obstructing stone may be
fragmented.
- Enlargement hydronephrotic
non functioning kidney.
- Fat globules

62. Angiomyolipoma
Homogeneous, highly echogenic,
usually rounded lesion in the renal
parenchyma containing blood
vessels, muscle tissue and fat.
Asymptomatic, if large causing
haematuria and pain.
Usually solitary, if multiple
bilateral, is associated with tuberose
sclerosis

63. Renal cell carcinoma (RCC)
Large, heterogeneous mass which
enlarges and deforms the shape of the
kidney.
The mass may contain areas of cystic
degeneration and/or calcification.
It has a predilection to spread into the
ipsilateral renal vein and IVC.
Colour Doppler usually reveals a
disorganized and increased blood flow
pattern within the mass.

64. Pelvi-calyceal tumor (TCC)
Most common in bladder, less
frequently in the collecting system of the
kidney and the ureter.
It is best diagnosed with cystoscopy.
Small, homogenous (compared to the
RCC) and relatively Hypoechoic.
Colour Doppler usually reveals
hypovascular blood flow pattern within
the mass.

65. Acute Tubular Necrosis
Acute tubular necrosis is the result of
ischemia and lead to acute renal failure.
Rapid reduction of kidney function and urine,
reversible if treated.
The kidneys often appear normal in acute
tubular necrosis (ATN) but may:
- Increased kidney size.
- Increased parenchymal echogenicity.
- Increased corticomedullary differentiation.
- Increased resistive index .

66. Glomerulonephritis
Inflammatory condition affects the glomeruli of the
kidney.
It may be either acute or chronic.
Patients may present in acute renal failure, with
oliguria or anuria, or with features of nephrotic
syndrome such as oedema, proteinuria and
hypoalbuminaemia.

67. Glomerulonephritis
In the acute stages:
- The kidneys may be slightly enlarged.
- Changes in the echogenicity of the
cortex may be observed.
In the chronic stages:
- The kidneys shrink.
- Become hyperechoic.
- loss of cortical thickness.
- Loss of corticomedullary
differentiation.

68. 1- Renal artery stenosis.
2- Renal vein thrombosis.
3- Renal vascular malformations.
Vascular Lesions

69. Mostly due to atherosclerotic disease, or to fibromuscular
dysplasia of the arterial wall in the younger, generally
female patient.
Cause hypertension and may eventually cause renal
failure.
At the site of a stenosis, an increase in peak systolic
velocity may be found (greater than 1.5–1.8 m/s) with
poststenotic turbulence
Renal Artery Stenosis (RAS)

70. Renal Artery Stenosis (RAS)

71. Renal Artery Stenosis (RAS)

72. It is often possible to see echo-poor thrombus within
a dilated renal vein.
Colour Doppler confirms absent venous flow.
Perfusion within the kidney itself is reduced.
 Highly pulsatile arterial waveform with reversed
diastolic flow.
If the thrombus produces a total and sudden
occlusion, the kidney becomes oedematous and
swollen within the first 24 h. Eventually it will shrink
and become hyperechoic.
Renal Vein Thrombosis

73. Renal Vein Thrombosis

74. localized vessel enlargement
with turbulent, sometimes
high-velocity flow.
A ‘pool’ of colour flow is
often present.
If bleeding is a clinical
problem and is ongoing,
recurrent and/or severe then
embolization is the
treatment of choice.
Renal Vascular Malformations

75. Renal Vascular Malformations

76. •Usually heterotopic
(placed in addition to the
native diseased kidneys)
•Positioned in the extra-
peritoneal pouch in the
iliac fossa (usually the
right) anterior to the
iliacus and psoas muscles.
Renal Transplant

77. THE ROLE OF ULTRASOUND (B Mode imaging)
 •Morphological appearances:
PC dilation
Peri-renal fluid collections
 •Doppler:
Colour /Power Perfusion
Spectral Doppler Waveforms
 •Intervention:
Guide Biopsy Procedures
Drain Fluid Collections
Placement of Nephrostomy
Tubes .
Renal Transplant

78. Renal transplant
Morphological appearances: echogenicity of
the cortex, medulla and renal sinus and
corticomedullary differentiation.
Size Changes in renal size may be significant in
transplanted organs; it is useful to calculate the
renal volume, circumference or area.
PCS dilatation: Degree of hydronephrosis.

79. Renal transplant
Vascular anatomy: global perfusion can be
assessed with colour Doppler.The normal
spectral Doppler waveform is a low-resistance
waveform with continuous forward end diastolic
flow.
Perirenal fluid: common complication either
resolve spontaneously or need drainage.

80. Renal Transplant

81. Post Transplant Complication
 Complications can be divided into three main categories: immediate
postoperative complications, primary and secondary renal
dysfunction.
 ● Immediate
—Non-perfusion, normally the result of an occluded or twisted renal
artery; correction is surgical
—Haematoma.
 ● Primary dysfunction
—Non-perfusion (arterial occlusion), total or lobar
—Acute tubular necrosis
—Renal vein thrombosis
—Obstruction.
—Acute or accelerated acute rejection

82. Post Transplant Complication
● Secondary dysfunction
—Acute rejection
—Cyclosporin nephrotoxicity
—Acute tubular necrosis
—Obstruction
—RAS
—Postbiopsy fistula
—Infection
—Chronic rejection.

83. Renal Transplant Rejection
This can be acute or chronic.
 Acute rejection: delayed graft
function.
Sonographic appearance:
-Enlargement due to oedema.
-Increased corticomedullary
differentiation with prominent
pyramids.
-Decreased fat in the renal sinus.

84. Renal Transplant Rejection
Chronic rejection: gradual deterioration
in renal function that may begin any time
after 3 months of transplantation.
Sonographic appearance:
-increase in the echogenicity of the
kidney.
-Reduced corticomedullary
differentiation.
- kidney will shrink.
-The Doppler resistance indices are
increased in rejection but this finding is
non-specific.

85. Renal Transplant Rejection

86. Procedural Applications of
Ultrasound in Nephrology

87. Procedural Applications of
Ultrasound in Nephrology
1- Percutaneous Renal Biopsy.
2- Catheter placement in heamodialysis patient.
3-Drainage of collections
4-cyst Aspiration..

88. Percutaneous Kidney Biopsy
The entry site, angle, and depth can be determined
with ultrasound, after which the needle is placed
without direct ultrasound guidance (ultrasound
marking), or ultrasound can be used during the
needle insertion (real-time guidance).

89. Summary & Take-Home Points
US is an adjunct in the evaluation of patients
with suspected renal colic
 Evaluate kidneys
 Evaluate aorta
Scan both kidneys

90. THANK YOU