The reasoning
| Anomaly | Imaging and pearls |
|---|---|
| Horseshoe kidney (commonest fusion anomaly) | lower poles fused by an isthmus anterior to the aorta and IVC, below the IMA (ascent arrested); low position, malrotated (renal pelves anterior), calyces point medially, lower‑pole calyces medial to the ureters ("hand‑shake"/"flower vase" ureters on IVU); complications: PUJ obstruction, stones, infection, trauma (isthmus over spine), Wilms' tumour, TCC; Turner syndrome, trisomy 18 |
| Crossed fused renal ectopia | both kidneys on one side, fused (lower pole of the orthotopic kidney fused with the upper pole of the crossed one); the crossed ureter crosses the midline to enter the bladder normally |
| Pancake (discoid) kidney | both kidneys fused into a single pelvic mass |
| Pelvic/ectopic kidney | commonest ectopia; malrotated, anomalous vessels |
| Renal agenesis | absent kidney + compensatory hypertrophy; ipsilateral genital anomalies (seminal vesicle cyst: Zinner syndrome in men; uterine anomalies/OHVIRA in women); confirm an "absent" kidney is not ectopic or non‑functioning (US/CT/DMSA); bilateral → Potter sequence |
| Supernumerary kidney | rare |
| Persistent fetal lobulation | smooth indentations between calyces (vs scars over calyces) |
| Column of Bertin (hypertrophied) | normal cortex projecting into the sinus; enhances like cortex (pseudotumour) |
| Dromedary hump | left lateral bulge (spleen impression) |