| disease | Perinephric Abscess |
Perinephric abscesses primarily result from the rupture of an intrarenal abscess into the perinephric space. Therefore, the causative organisms are the same as those that cause intrarenal abscesses. In approximately 25% of cases, the abscess may yield multiple pathogenic organisms on culture. The perinephric fascia typically confines the abscess to the area around the kidney, and the disease-causing factors are the same as those for intrarenal abscesses.
bubble_chart Clinical Manifestations
Perirenal abscess has an insidious onset and lacks specific clinical manifestations, making early diagnosis extremely difficult. Symptoms typically appear 2–3 weeks before patients seek medical attention. Even after seeking care, diagnosis may be delayed for several days. Fever is the most common symptom, but it is often initially attributed to an unknown cause. Key signs include pain or tenderness in the lumbar or costovertebral angle region, with or without a palpable abdominal or lumbar mass.
The diaphragm on the affected side may be elevated or fixed, with or without pleural effusion. Additionally, patients may experience chest pain. Psoas muscle spasm often leads to scoliosis (concave toward the affected side), causing pain when the patient bends forward. A painful lumbar mass and skin erythema are signs of an advanced stage of perirenal abscess.
bubble_chart Auxiliary Examination
Laboratory tests: Routine laboratory test results are varied and inconsistent. Blood tests may reveal elevated white blood cells with a left shift, varying degrees of anemia, and an increased erythrocyte sedimentation rate. Serum creatinine and blood urea nitrogen may only rise if the patient has other kidney diseases or bilateral lesions. Urinalysis shows pyuria and proteinuria but no hematuria. In 30% of patients, urine analysis is normal, 40% have negative urine cultures, and only 40% show positive results in blood cultures.
X-ray examinations: Although chest and abdominal X-rays cannot definitively diagnose perinephric abscesses, they can aid in diagnosis. Chest X-rays may reveal ipsilateral diaphragmatic elevation and fixation, pleural effusion, empyema, lung abscess, lower lobe infiltrates, atelectasis, or pneumonic scarring. Abdominal X-rays may show scoliosis (concave toward the affected side), masses, kidney stones, loss of normal renal or psoas muscle contours, gas in or around the kidney, or a fixed kidney.Imaging studies: In most cases of perinephric abscesses, excretory urography with tomography can confirm abnormalities in the affected kidney. Key findings include poor or absent contrast excretion, masses, renal displacement, renal or ureteral stones, and calyceal dilation or obstruction (with or without stones). However, none of these imaging features are specific to perinephric abscesses.
Gallium (Ga67) citrate or indium (In111)-labeled white blood cell radionuclide scans have limited diagnostic value, as they are time-consuming and cannot differentiate perinephric abscesses from other renal diseases. Renal arteriography is also not a specific diagnostic method for perinephric abscesses, as it is invasive and offers no advantage over renal ultrasound or CT scans. Therefore, arteriography is rarely used for diagnosing perinephric abscesses.
Renal ultrasound is a diagnostic tool for perinephric abscesses, but CT scans provide a more comprehensive view of the condition. CT findings include soft tissue masses with attenuation values reduced to 0–20 Hounsfield units (HU). Without contrast enhancement, the inflammatory abscess wall may show slightly lower attenuation. After contrast injection, the abscess wall enhances, surrounding tissue planes blur, the affected kidney or psoas muscle enlarges, the perinephric fascia thickens, and gas or air-fluid levels may appear within the lesion. Percutaneous aspiration under CT guidance can confirm the diagnosis and identify the causative organism.
Antibiotic treatment alone is often ineffective and should be combined with early and thorough drainage. Traditional treatment advocates incision and drainage of the abscess. In recent years, for certain cases, percutaneous placement of an appropriately sized drainage tube under ultrasound or CT guidance has also yielded satisfactory results. If percutaneous drainage fails, timely incision and drainage or nephrectomy must be performed.
Before the results of bacterial culture and drug sensitivity tests are available, antibiotic treatment targeting the most likely pathogens (Staphylococcus, Escherichia coli) should be initiated. The choice of drugs and dose are consistent with the treatment of intrarenal abscesses. Subsequently, adjustments can be made based on clinical response and drug sensitivity tests. Until clinical or imaging evidence confirms complete resolution of the infection, intravenous or later-stage oral antibiotic therapy is necessary, often lasting several weeks.
If diagnosed promptly and treated effectively, the patient's prognosis is good; mortality is associated with delayed diagnosis and inappropriate treatment.
