An obstructed kidney with infection behind the blockage is a urological emergency. Antibiotics cannot reach pus trapped behind a stone. The patient needs urgent decompression, by a nephrostomy or a ureteric stent, as well as antibiotics. The bedside scan does not prove pus, but it can move this patient up the queue.
Scan images in the graphic are illustrations, not patient scans.
The scan
- Use the curvilinear probe in the flank, with the patient supine or turned slightly.
- Find the kidney in long axis, then sweep through it from one edge to the other.
- Turn 90° and sweep in short axis.
- Scan the other kidney and the bladder for comparison.
- If you see echoes in the collecting system, reduce the gain and switch on tissue harmonics, then look again.
- Ask the patient to roll a little. Debris shifts to the dependent side. Artefact does not.
Reading the view
- Simple hydronephrosis. A black, branching collecting system which connects with the renal pelvis. The fluid is clear.
- Pyonephrosis. The same dilated system with internal echoes: floating debris, low-level echoes or a fluid-debris level with the debris lying dependent. Bright spots with dirty shadowing suggest gas, which is rarer and more dangerous.
- The whole picture. A stone at the pelviureteric junction or in the ureter, a temperature, rigors or hypotension. The decision rests on obstruction plus sepsis.
