Renal Corticomedullary Abscess - An Overview

Introduction

A renal corticomedullary abscess is a range of diseases that include numerous intrarenal infectious processes that include:

• Renal cortical abscess.

• Proper renal corticomedullary abscess.

• Acute focal bacterial nephritis.

• Acute multifocal bacterial nephritis.

• Emphysematous pyelonephritis.

• Xanthogranulomatous pyelonephritis.

Initially, it was considered that renal corticomedullary abscess was a sequel of urinary tract infections where the bacteria travel up the urinary tract. However, renal cortical abscess or renal carbuncle was caused by the hematogenous spread of bacteria.

Adults' common susceptible risk factors are nephrolithiasis, diabetes mellitus, and ureteral obstruction. In children, the predisposing risk factors are urologic anomalies such as vesicoureteral reflux, ureteropelvic junction obstruction, calyceal diverticulum, and urolithiasis. Although kidney and perirenal infections are rare if left undiagnosed, they carry the risk of morbidity and mortality. Investigations include imaging studies.

What Are the Causes of a Renal Corticomedullary Abscess?

A renal corticomedullary abscess is caused by enteric gram-negative bacilli infection, often associated with urinary tract abnormalities. E coli causes 75 % of these infections, and 15 % to 20 % of the cases are caused by proteus, Enterobacter, Klebsiella, and Serratia species. The remaining cases of renal corticomedullary abscess are caused by gram-positive bacteria, which include Streptococcus faecalis and Streptococcus aureus (less common).

A renal corticomedullary abscess is seen in association with the following urinary tract abnormalities:

• Vesicoureteral reflux.

• Urinary tract obstruction.

A renal corticomedullary abscess is common in individuals with diabetes mellitus, whether they have a urinary tract obstruction or not.

The risk factors mentioned below are partly responsible for subsequent renal corticomedullary abscesses:

• Urinary Tract Infections: The causative agents of urinary tract infections are enteric gram-negative bacteria for individuals of all ages. The bacterial pathogens travel toward the upper tract and transmit the infection to the renal medulla. Successive liquefaction of renal parenchyma and involvement of the renal cortex is responsible for renal corticomedullary abscess.

• Renal Calculi: 30% of the individuals with renal corticomedullary infections have nephrolithiasis. The individuals often also present with recurrent urinary tract abscesses, which lead to bacterial seeding of the renal calculi. Long-established infections with proteus, pseudomonas, and klebsiella cause the formation of struvite stones. Struvite stones are made of magnesium, ammonium, and phosphate. The existence of an infection nidus provides a suitable environment for ascending infection.

• Genitourinary Instrumentation: Urologic procedures such as endopyelotomy or ureteroscopy may lead to obstruction and ureteral stricture. Two-thirds of the individuals with a renal corticomedullary abscess had a prior procedure of urinary instrumentation.

• Vesicoureteral Reflux: The function of the ureterovesical junction is to prevent the backward flow of urine to the kidney and assist urine flow into the bladder. This prevents the kidney from getting infected by urine. When the ureteropelvic junction is unproficient, there is an increased risk of ascending urinary tract infections. The pathology of vesicoureteral reflux is a weak detrusor followed by a combination of a short intramural tunnel of the ureter leading to lowered resistance pressure to reflux. Causes of vesicoureteral reflux include congenital trigonal weakness or complete ureteral duplication with refluxing lower pole moiety, poorly compliant neurogenic bladder, or vesical refluxing caused due to high-pressure bladder. In addition, refluxing infected urine causes hypertension, pyelonephritis, and nephropathy corticomedullary abscess.

• Diabetes Mellitus: Half of the individuals affected with renal corticomedullary abscess have diabetes mellitus. Aspects predisposing to intrarenal abscess among individuals with diabetes mellitus involve diabetic cytopathic, diabetic neuropathy, and impaired leukocyte function.

• Splenectomy: Splenectomy correlates with renal and perinephric abscesses, especially comorbid with diabetes mellitus.

What Is the Epidemiology of Renal Corticomedullary Abscess?

The occurrence of renal corticomedullary abscess scales from 1 to 10 cases per 10,000 hospital admissions. Pyelonephritis rarely leads to a renal corticomedullary abscess. Renal corticomedullary abscess shows a male predominance in almost 75 % of the cases. Nevertheless, renal corticomedullary abscess cases are rare without risk factors.

What Is the Prognosis for Renal Corticomedullary Abscess?

The renal corticomedullary abscess has a mortality rate of 1.5 % to 15 %. The prognosis is better with early diagnosis and treatment.

Factors that result in poor prognosis are:

• Urosepsis.

• Advanced age.

• Anatomic abnormalities.

• Advanced disease.

• Impaired renal function.

Physical Examination and Symptoms:

Common signs and symptoms include:

• Fever.

• Chills.

• Nausea or vomiting.

• Flank pain.

• Abdominal pain.

Nonspecific constitutional symptoms include:

• Malaise.

• Fatigue.

• Weight loss.

• Abscess formation.

• Reno-cutaneous fistula.

• Reno-colonic fistula.

• Reno-bronchial fistula.

Individuals with renal corticomedullary abscesses have long-standing symptoms. Regrettably, these symptoms are vague and do not show the severity of the condition. Most individuals with renal corticomedullary abscesses have a medical history of recurrent urinary tract infections, renal calculi, or prior genitourinary tract infection. Urinary tract obstruction is a major predisposing factor. Physical examination shows signs of infection, ill appearance, fever, hemodynamic or overall instability, tachycardia, hypotension, tachypnea, palpable masses, and costovertebral angle tenderness.

What Is the Treatment for Renal Corticomedullary Abscess?

Acute focal and multifocal pyelonephritis is treated with antibiotic therapy, which responds within a week. Large abscesses do not respond to antibiotics alone and need intervention. Renal abscess lesions less than 3 cm can be treated with antibiotic therapy. Medical treatment should be specific to hemodynamically stable patients with lesions smaller than 3 cm (centimeter). Management for hemodynamically unstable individuals with renal abscesses larger than 3 cm may have to undergo percutaneous or surgical drainage.

Surgical Modalities:

Surgical drainage, debridement, and nephrectomy were once the gold standard for renal corticomedullary abscesses. However, with newer antibiotics and percutaneous techniques, the surgical approach is now limited to only severe or refractory cases of renal corticomedullary abscesses.

Severe cases involve:

• Unresponsive to antibiotics.

• Impending sepsis.

• Hemodynamic instability.

• Coagulopathy.

Surgical approaches involve:

1. Abscess drainage is done in individuals with a persistent fever with no clinical improvement even after a week of antibiotic therapy.

2. Surgical therapy is done after the abscess is explored and drained.

3. Nephrectomy is performed in individuals with diffusely damaged renal parenchyma or sepsis.

Conclusion

A renal corticomedullary abscess is a range of diseases. Kidney and perirenal infections are rare, but they carry the risk of morbidity and mortality. Treatment involves antibiotic therapy and surgical approaches for severe cases.