Perinephric abscesses are not uncommon; they are usually caused by staphylococci, and arise from a small metastatic abscess in the cortex of the kidney, which may be solitary, or one of many pyaemic abscesses.
The patient, who may be any age, presents with fever and a tender swollen area in his loin or subhepatic area. If his abscess is small and related to the upper pole of his kidney, he may have no localizing signs. The approach to the kidney is the same as that for a nephrostomy, so see Section 23.13, and particularly Fig. 23-16.
PERINEPHRIC ABSCESS X-RAYS. Take a plain X-ray. Look for obliteration of the patient's psoas shadow, and scoliosis with a concavity towards the abscess. Look also for disease of his spine, especially narrowing of intervertebral discs and erosion of the bodies of his vertebrae nearby, especially anteriorly (osteomyelitis, an important differential diagnosis).
Screen the movement of his diaphragm. This is reduced in most cases of subphrenic abscess, but seldom with perinephric abscesses.
An IVU shows a normally functioning kidney which may be displaced, especially medially or posteriorly.
CAUTION ! An intravenous urogram is essental. Without one you cannot exclude a pyonephros.
DIFFERENTIAL DIAGNOSIS. (1) Pyomyositis of the abdominal wall or paraspinal muscles. (2) Pyonephros. (3) Subphrenic abscess. (4) Osteomyelitis of the spine, with spread to the paraspinal tissues.
MANAGEMENT. His pus must be drained. You may not know for certain if it is perinephric, subphrenic (especially in the posterior or subhepatic spaces), or has spread from osteitis of his spine.
ANTIBIOTICS. Give him an antibiotic (chloramphenicol or a cephalosporin, 2.9).
ANAESTHETIC. (1) General anaesthesia with intubation. (2) Intravenous ketamine.
POSITION. Lie him in the kidney position as for a nephrostomy[md]see Section 23.13.
INCISION. Make a 15 to 20 cm incision starting posteriorly over his 12th rib just lateral to his sacrospinalis muscle (about the mid point of the rib). Cut down on the rib, incise and deflect the periosteum, so as to push the nerves and vessels aside. Remove the distal two thirds of his rib and dissect through its bed to expose his perinephric space containing the abscess.
If the pus is in his muscles (pyomyositis), you will discover this before you reach his rib (unless it is in his psoas or quadratus lumborum). If it is spreading from his spine or is subphrenic, you will also find it.
Drain the pus by Hilton's method (5-3). Insert a wide bore tube or corrugated drain and close the wound in layers.
Fig. 5-9a A PERINEPHRIC ABSCESS. A, an unusually large perinephric abscess. B, approach a perinephric abscess through the bed of the 12th rib. C, put the patient into the left lateral position. D, the true renal capsule is closely applied to the surface of the kidney. Outside this, the perinephric fat is surrounded by the perinephric fascia (Gerota's fascia). After Robert C Flanigan in Rob's ''Operative Surgery'. Figs. 1b, 3, and 12a. With the kind permission of Hugh Dudley.