Renal infection
| Entity | Imaging |
|---|---|
| Acute pyelonephritis | imaging not needed in uncomplicated cases; CECT: wedge‑shaped/striated nephrogram (alternating bands), swollen kidney, perinephric stranding; DMSA: cortical defects |
| Renal / perinephric abscess | rim‑enhancing collection; drain if > 3–5 cm |
| Emphysematous pyelonephritis | gas in the renal parenchyma (CT IOC), diabetics (~90%), E. coli; class 1–4 (Huang & Tseng); emergency (drainage/nephrectomy) |
| Emphysematous pyelitis | gas only in the collecting system (better prognosis) |
| Xanthogranulomatous pyelonephritis | enlarged kidney, staghorn calculus, dilated calyces with low‑density lipid‑laden contents: bear paw sign; poorly functioning; mimics tumour |
| Renal tuberculosis | papillary necrosis, moth‑eaten calyx, infundibular strictures (phantom calyx), hydrocalyx, "Kerr kink" (pelvic kinking), amputated calyx, thimble bladder (contracted), "putty kidney"/autonephrectomy (dense calcification of a non‑functioning kidney), ureteric strictures: beaded / corkscrew / pipe‑stem ureter |
| Papillary necrosis | ring sign, ball‑on‑tee, lobster claw (analgesics, diabetes, sickle cell, TB, obstruction, pyelonephritis) |