Treatment consists of i.v. antibiotics (as for pyelonephritis), i.v. fluids, and percutaneous nephrostomy insertion.
FIGURE 3.11. a: The appearance of a pyonephrosis on ultrasound. Note the hyperreflective material within the dilated system. b: A right pyonephrosis on CT, done without contrast. Note the presence of a stone in the kidney. c: A right pyonephrosis on CT postcontrast administration.
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FIGURE 3.11. Continued
38 J. REYNARD
FIGURE 3.12. A left perinephric abscess as seen on CT. PERINEPHRIC ABSCESS
Perinephric abscess (Fig. 3.12) develops as a consequence of extension of infection outside the parenchyma of the kidney in acute pyelonephritis, or more rarely, nowadays, from haematoge-nous spread of infection from a distant site. The abscess develops within Gerota's fascia—the fascial layer surrounding the kidneys and their cushion of perinephric fat. These patients are often diabetic, and associated conditions such as an obstructing ureteric calculus may be the precipitating event leading to development of the perinephric abscess. Failure of a seemingly straightforward case of acute pyelonephritis to respond to intravenous antibiotics within a few days should arouse your suspicion that there is something else going on, such as the accumulation of pus in or around the kidney, or obstruction with infection. Imaging studies, such as ultrasound and more especially CT, will establish the diagnosis and allow radiographically controlled percutaneous drainage of the abscess. However, if the pus collection is large, formal open surgical drainage under general anaesthetic will be provide more effective drainage.
This is a rare and severe form of acute pyelonephritis caused by gas-forming organisms (Fig. 3.13). It is characterised by fever
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FIGURE 3.13. a: A case of emphysematous pyelonephritis on plain abdominal x-ray. Note the presence of gas within the left kidney. b: A CT of the same case. The gas in the kidney (like that in the bowel) is black on CT. c: A percutaneous drain has been inserted with the patient lying prone. Note the J loop of the drain in the kidney.