Renal abscesses may be localized to the renal cortex (renal car-buncle) or extend into the fatty tissue around the kidney (per-inephric abscess). The incidence of renal abscesses ranges from 1 to 10 cases per 10,000 hospital admissions.
A renal abscess may be caused by an infection of the kidney (pyelonephritis) or may occur as a hematogenous (spread through the bloodstream) infection originating elsewhere in the body. Of-fending organisms include Staphylococcus and Proteus species and E. coli. Occasionally, infection spreads from adjacent areas, suchas with diverticulitis or appendicitis.
The manifestations of a perinephritic abscess often are acute in onset, with chills, fever, leukocytosis, a dull ache or palpable mass in the flank, abdominal pain with guarding, and CVA tenderness on palpation. The patient usually appears seriously ill.
The patient with a renal abscess may report a recent history of a cutaneous boil or carbuncle and may complain of malaise, fever, chills, anorexia, weight loss, and a dull pain over the kidney. Leukocytosis and sterile urine (no microorganisms seen because the infection does not extend into the urinary collection system) are present with renal abscesses localized to the renal cortex. The CT examination results are important both in the diagnostic phase to establish the extent of the lesions and in the follow-up phase to assess the effectiveness of treatment (Dalla Palma, Pozzi-Mucelli & Ene, 1999).
Small localized abscesses are usually cured by intravenous anti-biotic medications alone but may require incision and drainage. Perinephritic abscesses require percutaneous drainage of the ab-scess. Culture and sensitivity tests are performed, and appropri-ate antibiotic therapy is prescribed. Drains are usually inserted and left in the perinephric space until all significant drainage has ceased. Because the drainage is often profuse, frequent changes of the outer dressings may be necessary. As in treating an abscess in any site, the patient is monitored for sepsis, fluid intake and out-put, and general response to treatment. Surgery may be indicated for extensive perinephritic abscesses.