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Renal Ultrasound

Echogenic renal sinus, anechoic collecting system. Kidney consists of lobes, each lobe contains a calyx, a medullary pyramid, cortical tissue and vessels. Adults: 11 pyramids, 9 calyces. Persistent fetal lobulation.

Column of Bertin

A prominent column of cortical tissue protrudes into the renal sinus in mid third. If it completely separates collecting system ==> Duplication

Weigert-Mayer rule

Upper pole Obstructs (UO), Lower pole Reflux (LR). Upper pole moiety ureter inserts ectopically distal and medial (DM) in the bladder wall, frequently with ureterocele. Lower pole moiety inserts proximal and lateral.

Congenital anomalies


  1. Grade 1: minimal distention

  2. Grade 2: moderate visible dilatation

  3. Grade 3: severe dilatation w/ cortical thinning

DDx: Hydronephrosis: Obstruction (Stone, TCC, Prostatic hypertrophy, Gynecologic masses, Bladder tu), VUR, Diabetes insipidus, Overdistention of bladder, Pregnancy, Extrarenal pelvis

The Society for Fetal Urology - SFU - US grading system for postnatal hydronephrosis

Renal Cysts

Most common renal mass, present in 50% above 50yrs. Sono is the most accurate way to eval renal cysts.

Simple renal cyst

Hemorrhagic renal cyst

Diffuse low level internal echoes, Fibrinous membranes, Internal echogenic clots --> may overlap w/ cystic RCC ⇒ CT or MRI for further evaluation

Calcifications in renal cyst

DDx: Renal cysts: Caliceal Diverticula, Papillary Necrosis, Obstructed upper pole duplications, Lymphoma; Peripelvic cyst may be confused w/ hydronephrosis.

Polycystic Kidney Disease (PCKD)

A.k.a Autosomal Dominant Polycystic Disease, Adult Polycystic Kidney Disease: Liver (50%), Pancreas (5%), Cerebral Aneurysms (20%). Clinically apparent at 40's. HTN and renal failure.

Sono: Multiple, Variable sized Cortical and Medullary Cysts bilaterally, completely replacing parenchyma. Enlarged kidneys. Stones formation, crystals produce comet tail artifacts, hemorrhages. No significant mlg potential

Acquired Cystic disease

Pattern of PCKD in patients on long term dialysis. 6 x higher risk for RCC than general population.

von Hippel-Lindau disease

Diagnosis usually made by finding intracranial hemangioblastoma.

Tuberous Sclerosis

Mental Retardation, Seizures, Cutaneous lesions

Skeletal lesions, Cutaneous lesions

Renl Cell Carcinoma

90% of primary renal malignancies, surgical lesion --> partial nephrectomy (no bx). 50% are hyperechoic, 40% only slightly more echogenic than the renal parenchyma, 10% hypoechoic. Isoechoic are detected only when exophytic or distorting renal contour. Solid w/ scattered cystic components, 20% w/ calcs.

All solid renal masses should be assumed to be RCC. The only way to prove that solid mass is not an RCC is to document presence of FAT in the mass by nonenhanced CT or MRI.

Only 5% are cystic RCC --> cyst w/ multiple thick septations, thick or irregular wall or solid intramural nodule, blood flow within is strong evidence of malignancy (see Bosniak clasiffication).

RCC is a vascular tu (will enhance on post-contrast CT).


  1. Stage I: Confined to the kidney

  2. Stage II: Invasion of the perinephric fat

  3. Stage IIIA: Invasion of the renal vein

  4. Stage IIIB: Regional nodal mets

  5. Stage IIIC: Venous and nodal involvement

  6. Stage IVA: Invasion of adjacent organs

  7. IVB: distant mets

Sono can identify venous invasion, specially IVC

Medullary Carcinoma

Variant of RCC, pt w/ sickle cell trait, much worse prognosis

DDx: Solid renal masses: RCC, Angiomyolipoma, TCC, Oncocytoma, Lymphoma, Mets, Juxtaglomerular cell tu, Column of Bertin, Focal pyelonephritis, Focal parenchymal hypertrophy

Transitional Cell Carcinoma (TCC)

90% of urothelial tu, 10% SCC. IVP.

DDx: Intraluminal polypoid mass: TCC, Blood clots, Fungus ball, Fibroepithelial polyps, Malakoplakia, Calculi


Multiple b/l hypoechoic masses, may simulate cyst but lack of acoustic enhancement

Renal Mets

Lung, Colon, Breast, Stomach, Prostate, Pancreas and Melanoma


Contains vessels (angio), muscles (myo) and fat (lipoma), most common bng neoplasm, middle-aged women. No mlg potential, bleeding if > 4 cm

Sono: Homogeneous, well defined cortical echogenic as renal fat lesion. 10% of RCC may have similar appearance. Some degree of acoustic shadowing (not seen in RCC unless calcs). Usually no cysts (RCC may have cysts) ⇒

Hyperechoic mass without partial shadowing requires further evaluation (CT or MRI should be able to detect fat). If fat is not detected on CT or MRI in a lesion larger than 1cm, RCC should be a strong consideration.

Crystal filled cysts may mimic AML and will produce ring-down artifact, not seen w/ AML.


Renal Adenoma, 5%, appearance overlaps w/ RCC. Stellate central scar on CT, surgical dx → partial nephrectomy

Juxtaglomerular Cell Tumor

Rare, Reninoma, young women, severe HTN. Hyperechoic

Multilocular Cystic Nephroma

Multiple, Large, Non-communicating cysts. Young boys and older women. Similar appearance w/ cystic RCC (older women) and cystic Wilms tu ⇒ partial nephrectomy

DDx: Complex cystic renal masses: Hemorrhagic cyst, Infected cyst, Multiseptated cyst, Abscess, Hematoma, Cystic RCC, Multilocular Cystic Nephroma


Process extends from the papilla to the periphery of the cortex in a patchy manner.

Sono: urothelial thickening of renal pelvis and infundibulum, renal enlargement, look for renal or perinephric abscess (complex fluid collections with internal echoes), obstruction, stones. Areas of both increased and decreased echogenicity which may be isolated or multifocal → patchy appearance to the cortex. Decreased perfusion from vasoconstriction. Abscess may need percutaneous drainage

Xanthogranulomatous Pyelonephritis

Chronic inflammatory process associated w/ long standing urinary obstruction. Proteus mirabillis, E.Coli. Staghorn calculus. Bear paw appearance. Radiologic triad: Stone, Renal enlargement, Lack of function

Emphysematous Pyleonephritis

DM, woman, gas in renal parenchyma from E.Coli, dirty shadowing ⇒ nephrectomy

Renal Calculi

Men 3 x more than F, predisposition: UPJ obstruction, PCKD, caliceal diverticula, tubular ectasia, horseshoe kidney, Crohn’s d, myeloproliferative disorders; Ca++ containing stones 80% (Ca oxalate or Ca phosphate), uric acid stones 5%, cistine stones 5%; 10% of stones are struvite (Magnesium-Ammonium- Phosphate) or apatite (Calcium phosphate) → Staghorn calculi, assoc. w/ infections w/ Proteus, Pseudomonas, Staph.aureus, Klebsiella; twinkle artifact - Doppler short color ring-down artifact;

Medullary nephrocalcinosis

Calcifications of medullary pyramids due to

  1. Medullary Sponge Kidney (tubular ectasia)

  2. Renal Tubular Acidosis

  3. Hyperparathyroidism

Renal Parenchymal Disease

Medical Renal Disease --> parenchyma more echogenic than the liver. Scanned due to ARF, perinephric fluid. Role of US is to exclude urinary obstruction and determine renal size

Renal Trauma

Contrast enhanced CT is superior to US. Renal and subcapsular hematomas --> globular kidney (Page kidney), increased renal vascular resistance due to compression of the renal parenchyma → to and fro waveforms w/ pandiastolic reversal


Renal artery branches into multiple segmental arteries, then interlobar arteries and arcuate arteries. Pulsed Doppler waveforms from the renal artery shows low-resistance pattern. Left renal artery is 3 x longer than the right, retroaortic or circumaortic left renal vein is present in 15%.

Renal Artery Stenosis

Atherosclerosis and FMD. Focal areas of aliasing and localized perivascular tissue vibration, peak systolic velocity > 200 cm/sec. Fast before exam to avoid bowel gas. Parvus-tardus effect: slowed systolic upstroke --> blunting of the waveform from distal arteries due to proximal renal artery stenosis

Renal Vein Thrombosis

Most common cause of unilateral renal enlargement, no venous flow on Doppler → diminished arterial flow, high resistance arterial waveform, sometimes w/ pandiastolic flow reversal. If clot develops slowly → collateral develops


From trauma, frequent in renal transplants, a swirling pattern of internal blood flow, assoc. w/ AV fistula

AVF (AV fistulas)

Doppler: perivascular ST vibration; from trauma (percutaneous bx), high output cardiac failure

Renal transplants

Eval hydronephrosis and peritransplant fluid collections, Lymphoceles, Urinomas, Abscesses, Stenosis, Thrombosis, Pseudoaneurysm, AV fistulas, bx