Perinephric Abscess Treatment & Management

The mainstay of treatment for perinephric abscess is drainage. Antibiotics are mainly used as an adjunct to percutaneous drainage because they help to control sepsis and to prevent the spread of infection. When kidneys are not functioning or are severely infected, nephrectomy (open or laparoscopic) is the classic treatment for perinephric abscesses. Percutaneous drainage is relatively contraindicated in large abscess cavities that are filled with a thick purulent fluid. However, attempt percutaneous drainage as the first line of therapy in these patients. These individuals require close observation for signs of sepsis, and use serial CT scanning to confirm that the perinephric abscess cavity is draining.

Direct empiric antibiotics against common gram-negative organisms and Staphylococcus aureus. An antistaphylococcal beta-lactam agent (eg, nafcillin, cefazolin) and an aminoglycoside (eg, gentamicin) are appropriate choices for the initial treatment. After the culture report, the antibiotics can be adjusted accordingly. If the report is positive for pseudomonads, an antipseudomonal beta-lactam (eg, mezlocillin, ceftazidime) can be started. For infection with enterococci, ampicillin and gentamicin are the treatment of choice. Isoniazid, rifampin, and ethambutol are indicated for Mycoplasma tuberculosis, and fungal infections require amphotericin B.

Percutaneous drainage diagnostic aspiration under ultrasonographic guidance carries minimal morbidity. Therefore, a trial of percutaneous drainage should be the initial modality of treatment for perinephric abscess. This approach is contraindicated in the setting of bleeding diathesis and when a hydatid cyst may be present.

Advantages of percutaneous drainage include the following:

• Earlier diagnosis and treatment
• Avoidance of  general anesthesia and surgery
• Low cost
• Greater acceptance by the patient
• Easier nursing care

Similar to the results for other types of intra-abdominal abscesses, percutaneous drainage of the retroperitoneal abscess has a success rate of 76-90%. The success rate is higher for single unilocular abscesses than for multilocular abscesses (82% vs 45%).

Poor results are seen in the following situations:

• Presence of fungal infection
• Calcification of the wall of the mass
• Calcified debris within the mass
• Thick purulent drainage
• Multiloculated cavity
• Emphysematous changes in the kidney
• Markedly diseased nonfunctioning kidney
• Underlying diseases such as calculi and diabetes
• Infected hematoma

If percutaneous drainage is not effective in improving the patient's clinical situation, open surgical debridement with placement of large drains may be necessary.

Administer broad-spectrum intravenous antibiotics before the procedure. Under local anesthesia, a 22-gauge Chiba needle is passed percutaneously into the abscess cavity under ultrasonographic or CT guidance.

Approaching the abscess below the level of the 12th rib is important to prevent pneumothorax and empyema. One also should avoid the peritoneal cavity by choosing the access point medial to the posterior axillary line.

Once the abscess is located with a thin needle, aspiration is attempted using an 18-gauge needle. Fluid is drained from the abscess, and a sample is sent for aerobic, anaerobic, and fungal cultures.

At this time, a catheter (eg, 10F locking-loop catheter or a 12F or 14F double-lumen sump drain such as a Van Sonnenberg or Ring-McLean catheter) is placed into the abscess cavity. The double-lumen catheter helps decrease clogging and can be used for irrigation with isotonic sodium chloride solution or antibiotic solution.

If indicated, a separate tube is placed to drain the collecting system (ie, nephrostomy tube). This is needed if the patient has renal obstruction from a stone or stricture.

After approximately 5-7 days of percutaneous drainage, drainage from the abscess stops. However, if the amount of drainage is small in the beginning and then begins to increase or becomes clear, suspect a urinary fistula. Workup should include IVP and/or retrograde pyelography to rule out the presence of a urinary fistula. If such a fistula is present, urinary diversion is required in the form of an indwelling ureteral stent or percutaneous nephrostomy tube.

Prior to removal of the drainage tube, perform ultrasonography, CT scanning, or a contrast study. If the cavity has substantially decreased, the catheter can be removed.

For a persistent large cavity, sclerosing therapy is recommended. Generally, tetracycline or 95% alcohol is used for this purpose. Tetracycline is instilled into the cavity, and the tube is clamped for 15 minutes and then opened for drainage. The process is repeated on a weekly basis until the cavity is almost obliterated. The tube is removed at this time.

A potential concern is that if small cavities persist and remain colonized, sclerosing therapy may be ineffective. The mere presence of a large cavity does not necessarily mandate sclerosing therapy. Provided that the underlying cause of the perinephric abscess is treated, most cavities eventually self-obliterate.

Appropriate oral antibiotics are given throughout the drainage/sclerosant period and for 1-3 weeks after the drainage tube is withdrawn.

Follow-up examinations, with urine cultures, ultrasonography, or CT scanning, are performed at 1-month and 3-month intervals to rule out recurrent infection.

Recurrence after percutaneous drainage is relatively rare (1-4%). Surgical intervention is needed in 3-22% of cases.

If the fluid is thick and drains poorly or if the cavity is multiloculated, an open or laparoscopic operation is recommended for drainage and debridement.

Certain conditions, such as renal cortical abscess, enteric fistulas, or multilocular abscesses, may require immediate surgical intervention. ^[10]  After the perinephric abscess has been incised and drained through a retroperitoneal approach, search for the underlying problem.

Nephrectomy is reserved for the following situations:

• Emphysematous pyelonephritis
• Diffusely damaged parenchyma
• Older patients who are septic and require urgent intervention
• Intractable cases

Complications of perinephric abscess include the following:

• Bleeding
• Flank abscess
• Fistula formation to stomach, small bowel, duodenum, lung
• Subphrenic abscess
• Empyema
• Pneumonia
• Atelectasis
• Sepsis
• Possible rupture into peritoneum
• Possible perforation through diaphragm

A nephrocolonic fistula occurs if the abscess erodes into the adjacent part of the colon. The patient may present with bloody stool, diarrhea, passing of urine per rectum, and passing of fecal contents into the urine. If this fistula opens on to the skin, urine and feces are discharged through the nephrocolocutaneous fistula.