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Perinephric Abscess

Definition

A perinephric abscess is a collection of pus within the renal fascia. Review literature: (Angel et al, 2003) (Shu et al, 2004)

Etiology

Gram-negative Bacteria:

Perinephric abscesses are most common caused by gram-negative bacteria such as E. coli and Proteus. Perinephric abscesses with gram-negative bacteria usually result from rupture of a renal abscess with cortical location. Nephrolithiasis is a risk factor.

Staphylococci:

Before the antibiotic era, perinephric abscesses were often caused by the hematogenous spread of staphylococci. Today's risk groups for hematogenous spread of staphylococci: intravenous drug abuse, intensive care, dialysis patients, valvular heart disease and endocarditis.

Signs and Symptoms of a Perinephric Abscess

In contrast to a renal abscess, signs and symptoms of a perinephric abscess have a slow onset and are unspecific. Patients present usually with symptoms of more than one week, complaining about fever, flank pain or abdominal pain, night sweat and chills. More than 30% are afebrile.

Perinephric Abscess: Diagnostic Work-Up

Urine culture:

Urine culture is not sensitive and can identify the responsible bacteria in only 30%.

Laboratory tests:

Blood culture (positive in 50%). Blood count, coagulation tests (PTT, PT), CRP, liver enzymes, creatinine. In suspected urosepsis, determination of sepsis parameters such as blood gas testing, procalcitonin, AT III and fibrinogen.

Ultrasonography:

Sonographic signs for a perinephric abcess in renal ultrasound are a perirenal hypoechoic area, which may have inclusion of air (echogenic reflex with dorsal shadowing).

Computed tomography:

CT is the diagnostic test of choice [fig. perinephric abscess]. The perinephric abscess appears as a hypodense area. Air inclusion is possible. After administration of contrast media, there is an ring-like enhancement of the abscess capsule.

CT of a right-sided perinephric abscess: (left horizontal plane, right sagittal reconstruction). The patient complained about night sweats and fatigue, he had no flank pain or fever. With kind permission of Prof. Dr. K. Bohndorf, Augsburg.

Intravenous urography:

Intravenous urography is not very helpful in suspected perinephric abscess. If done, KUB x-ray may show an absent psoas shadow, a perinephric mass, retroperitoneal air surrounding the kidney and nephrolithiasis. The excretion of contrast media is often without pathological findings.

Treatment of a Perinephric Abscess

Treatment consists of parenteral antibiotics and abscess drainage:

• Parenteral antibiotics: e.g. amoxicillin and clavulaic acid 2,2 g 1–1–1 i.v. in combination with gentamicin 3 mg/kg 1–0–0 i.v. Alternatives are third generation cephalosporins.
• Abscess drainage: in most cases, percutaneous drainage is sufficient. Pus is sent for identification of bacteria and antibiotic resistance testing. In advanced disease, surgical drainage is necessary. Nephrectomy is rarely necessary in a nonfunctioning kidney with persisting sepsis despite maximal therapy.

References

Angel u.a. 2003 ANGEL, C. ; SHU, T. ; GREEN, J. ; ORIHUELA, E. ; RODRIQUEZ, G. ; HENDRICK, E.:

Renal and peri-renal abscesses in children: proposed physio-pathologic mechanisms and treatment algorithm.
In: Pediatr Surg Int
19 (2003), Nr. 1–2, S. 35–9

Shu u.a. 2004 SHU, T. ; GREEN, J. M. ; ORIHUELA, E.:

Renal and perirenal abscesses in patients with otherwise anatomically normal urinary tracts.
In: J Urol
172 (2004), Nr. 1, S. 148–50

  Deutsche Version: Perinephritischer Abszess