Arrange for a kidney and urinary bladder (KUB) x-ray and renal ultrasound, to see if there is an underlying upper tract abnormality (such a ureteric stone), unexplained hydronephro-sis, or (rarely) gas surrounding the kidney (suggesting emphyse-matous pyelonephritis).
3. NONTRAUMATIC RENAL EMERGENCIES 35
FIGURE 3.10. A CTU without contrast in a diabetic patient with left acute pyelonephritis. Note the incidental finding of a nonobstructing left renal calculus.
If the patient does not respond within 3 days to this regimen of appropriate intravenous antibiotics (confirmed on sensitivities), arrange for a CTU (Fig. 3.10). The lack of response to treatment indicates that you are dealing with a pyonephrosis (i.e., pus in the kidney, which like any abscess will respond only to drainage), a perinephric abscess (which again will respond only to drainage), or emphysematous pyelonephritis. The CTU may demonstrate an obstructing ureteric calculus that may have been missed on the KUB x-ray, and ultrasound and will show a per-inephric abscess if present. A pyonephrosis should be drained by insertion of a percutaneous nephrostomy tube. A perinephric abscess should also be drained by insertion of a drain percutaneously.
If the patient responds to i.v. antibiotics, change to an oral antibiotic of appropriate sensitivity when they become apyrexial, and continue this for approximately 10 to 14 days.
36 J. REYNARD
This is an infected hydronephrosis, the infection being severe enough to cause accumulation of pus with the renal pelvis and calyces of the kidney. The causes are essentially those of hydronephrosis, where infection has supervened. Thus, they include ureteric obstruction by stone and PUJ obstruction.
Patients with pyonephrosis are usually very unwell, with a high fever, flank pain, and tenderness. Again, a patient with this combination of symptoms and signs will usually be investigated by a renal ultrasound, where the diagnosis of a pyonephrosis is usually obvious (Fig. 3.11).