Diagnostic ultrasound ( PDFDrive )

CHAPTER 9 The Kidney and Urinary Tract 325
debilitated and immunocompromised patients. 30 his entity is
most frequently caused by Corynebacterium urealyticum, a ureasplitting
microorganism. Urothelial stone encrustation develops
in the kidney and bladder. If the kidney is afected, the patient
may present with hematuria, stone passage, or an ammonium
odor to the urine. Dysuria and suprapubic pain are the most
common clinical signs if the bladder is involved. Treatment is
with antibiotics and local acidiication of the urine. On sonography,
alkaline-encrusted pyelitis is suggested if thickened, calciied
urothelium is identiied. 30 he calciication can be thin and smooth
or thick and irregular. Care should be taken to distinguish
urothelial calciication from layering of collecting system calculi. 30
Renal and Perinephric Abscess
Untreated or inadequately treated acute pyelonephritis may lead
to parenchymal necrosis and abscess formation. Patients at
increased risk for renal abscesses include those with diabetes,
compromised immunity, chronic debilitating diseases, urinary
tract obstruction, infected renal calculi, and intravenous drug
abuse. 26,31 Renal abscesses tend to be solitary and may spontaneously
decompress into the collecting system or perinephric space.
Perinephric abscesses, also a complication of pyonephrosis,
may result from direct extension of peritoneal or retroperitoneal
infection or interventions. 24 Small abscesses are treated conservatively
with antibiotics, whereas larger abscesses oten require
percutaneous drainage and, if drainage is unsuccessful, surgery.
At ultrasound, renal abscesses appear as round, thick-walled,
hypoechoic complex masses with through transmission (Fig.
9.20). Internal mobile debris and septations may be seen. Occasionally,
“dirty shadowing” may be noted posterior to gas within
the abscess. he diferential diagnosis includes (1) hemorrhagic
or infected cysts, (2) parasitic cysts, (3) multiloculated cysts, and
(4) cystic neoplasms. Although not as accurate as CT in determining
the presence and extent of perinephric abscess extension, 26
sonography is an excellent modality for following conservatively
treated patients with abscesses to document resolution.
Pyonephrosis
Pyonephrosis implies purulent material in an obstructed collecting
system. Depending on the level of obstruction, any portion of
the collecting system, including the ureter, can be afected. Early
diagnosis and treatment are crucial to prevent development of
bacteremia and life-threatening septic shock. he mortality rates
of bacteremia and septic shock are 25% and 50%, respectively 32 ;
15% of patients are asymptomatic at presentation. 33 In the young
adult, UPJ obstruction and calculi are the most frequent cause
of pyonephrosis, whereas malignant ureteral obstruction is
typically the predisposing factor in older patients. 26 Pyonephrosis
is suggested when ultrasound shows mobile collecting system
debris (with or without a luid-debris level), collecting system
gas, and stones (Fig. 9.21).
Emphysematous Pyelonephritis
Emphysematous pyelonephritis (EPN) is an uncommon, lifethreatening
infection of the renal parenchyma characterized by
gas formation. 34 Most patients are women (2 : 1) and diabetic
(90%), with a mean age of 55 years. In diabetic patients, EPN
tends to occur in nonobstructed collecting systems; the reverse
is true in nondiabetic patients. Bilateral disease occurs in 5% to
10% of EPN patients. Escherichia coli is the ofending organism
in 62% to 70% of cases; Klebsiella (9%), Pseudomonas (2%) Proteus,
Aerobacter, and Candida are additional causative organisms. 26,31
At presentation, most patients are extremely ill with fever, lank
pain, hyperglycemia, acidosis, dehydration, and electrolyte
imbalance 35 ; 18% present only with fever of unknown origin. 36
Wan et al. 37 retrospectively studied 38 patients with EPN and
identiied two types of disease: EPN1, characterized by parenchymal
destruction and streaky or mottled gas, and EPN2,
A
B
FIG. 9.20 Renal Abscess. (A) Sagittal ultrasound shows a complex cystic upper-pole lesion containing layering low level echoes. (B) Corresponding
contrast-enhanced CT exam shows a large right upper-pole cystic lesion with a thick rind. The patient was successfully treated with ultrasound
guided drain placement and antibiotics.