Diagnostic Ultrasound - Abdomen and Pelvis

Hydronephrosis
Diagnoses: Urinary Tract
TERMINOLOGY
• Dilation of renal collecting (pelvicalyceal) system ± ureteral
dilation from intrinsic or extrinsic cause
• Renal collecting system dilation, pelvicalyceal dilatation,
pelvocaliectasis
IMAGING
• Dilated intercommunicating fluid-filled anechoic channels
(renal calyces and pelvis) in kidney
• Severity of hydronephrosis depends on degree and
duration of obstruction
• Presence of internal echoes within dilated collecting system
may represent underlying infection/pyonephrosis
• Antenatal US: Renal pelvis AP diameter ≥ 4 mm prior to 20-
week gestation
• Fetal renal pelvis diameter ≥ 7 mm at 20-28 weeks or ≥ 10
mm beyond 28-week gestation requires postnatal followup
KEY FACTS
• CT has high sensitivity in evaluating site and etiology of
obstruction (intrinsic [stone] or extrinsic)
• CT may show striated nephrogram &/or urothelial
enhancement in superadded infection (pyelonephritis)
• CT urogram: Useful in nonstone etiology (urothelial
neoplasm, necrosed/sloughed papillae, clot)
• MAG 3/DTPA scan: Central photopenic area at vascular
phase, tracer accumulation within hydronephrotic
collecting system with delayed drainage
TOP DIFFERENTIAL DIAGNOSES
• Parapelvic cyst
• Extrarenal pelvis
• Prominent renal vasculature
• Autosomal dominant polycystic kidney
PATHOLOGY
• Chronic obstruction: Loss of renal parenchyma and function
(Left) Axial transabdominal
renal ultrasound shows an
echogenic stone in the
renal pelvis with mild
hydronephrosis ſt. (Right)
Pulsed Doppler ultrasound in
the same patient with ureteral
stone shows elevated
resistive indices (RI) (1.0) ,
which indicates obstruction is
acute in nature. The
contralateral normal kidney
had a normal RI of 0.7 (not
shown), which is another
finding indicative of acute
obstruction in this kidney.
(Left) Longitudinal
transabdominal ultrasound of
the right kidney shows
moderate hydronephrosis as
evidenced by the presence of
caliectasis ſt as well as
pelviectasis . (Right)
Longitudinal transabdominal
ultrasound in a different
patient shows a moderately
dilated renal pelvis ſt with
echogenic debris , which
raises concern for
pyonephrosis in the proper
clinical setting of
superimposed infection.
Additional finding of a few
echogenic intracalyceal stones
may be nidus for infection.
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