Urinary: Infection Flashcards
Classic appearance of pyelonephritis on CT
- Striated nephrogram (best seen on excretory phase)
- Vague, focally reduced areas of enhancement with associated perinephric stranding
How can you differentiate between pyelonephritis and renal infarction on imaging?
Cortical rim sign:
Pyelonephritis classically involves a complete wedge of kidney extending through the cortex
Infarct classically involved a central wedge where there is a cortical rim of normally enhancing cortex peripherally
Pyelonephrosis
Pyelonephritis with obstruction
Note: A fluid-fluid level is often seen on ultrasound.
Differential for striated nephrogram
Things that cause hypoperfusion or edema:
- Acute ureteral obstruction
- Acute pyelonephritis
- Acute renal vein thrombosis
- Radiation nephritis
- Acutely following renal contusion
- Hypotension (would be bilateral)
- Infantile polycystic kidney (would be bilateral)
Treatment for pyelonephrosis
Urgent decompression with percutaneous nephrostomy
Treatment for renal abscess
IR-guided drainage (if >3 cm)
Spectrum of pyelonephritis
- Pyelonephritis (striated nephrogram)
- Lobar nephronia (phlegmon: ill-defined focal low density but not yet cystic, more common in pediatrics)
- Renal abscess (well-defined cystic core, usually with a thick enhancing rim)
CT appearance of chronic pyelonephritis
Renal scarring with atrophy/cortical thinning and hypertrophied residual tissue
Emphysematous pyelonephritis
Note: Perinephric echogenic line with dirty shadowing.
Emphysematous pyelonephritis is most common in what pt population?
Diabetics
Emphysematous pyelitis
When gas is limited to the collecting system (not as bad as emphysematous pyelonephritis)
Emphysematous pyelitis
Note: Gas limited to collecting system.
Common causes of papillary necrosis
- Diabetes (most common)
- Pyelonephritis
- Sickle cell disease
- Tuberculosis
- Analgesic use
- Cirrhosis
Renal papillary necrosis
Note: “Lobster claw sign” of the renal calyx.
Renal papillary necrosis
Note: Linear streaks/filling defects in renal calyces.
What percentage of pts with sickle cell disease develop renal papillary necrosis?
50%
Xanthogranulomatous pyelonephritis (in the setting of stag horn calculus)
Note: Characteristic “bear paw” appearance. This kidney is not functional.
Xanthogranulomatous pyelonephritis
A chronic destructive granulomatous process involving the kidney (virtually always seen in the setting of a stag horn calculus), giving a characteristic “bear paw” appearance on CT. The affected kidney is not function and sometimes treated with nephrectomy.
Pts with xanthogranulomatous pyelonephritis are at high risk for…
Psoas abscess
AIDS pt with nephrotic syndrome (massive proteinuria)…
HIV nephropathy
Note: Bilateral hyperdense kidneys (more dense than liver) in an AIDS pt with nephropathy.
Diagnosis of HIV nephropathy
Biopsy
Most common cause of renal impairment in AIDS pts
HIV nephropathy
HIV pt
Disseminated PCP infection
Note: Punctate cortical calcifications, appears the same as cortical nephrocalcinosis.
What is the most common extra-pulmonary site of tuberculosis?
Urinary tract
