What Is It, Causes, Diagnosis, Treatment, and More
Author: Lily Guo
Illustrator: Aileen Lin
What is a perinephric abscess?
A perinephric abscess is a collection of pus that occurs due to a bacterial infection in the perinephric fat and fascia surrounding the kidney. The kidneys are a pair of bean-shaped organs located under the ribs and behind the stomach, on either side of the spine. Each kidney is encapsulated in a fibrous capsule, known as the renal capsule, and contained in an area called the perinephric space. Within this space, the kidneys are surrounded by a layer of perinephric fat that protects them from damage. Encompassing the fat layer is a tough, fibrous connective tissue called the renal fascia. The renal fascia towards the anterior (front of the body), is also referred to as Gerota’s fascia. A perinephric abscess often affects the renal capsule, and can extend to Gerota’s fascia, the abdominal cavity, and the pelvis.
What is the perinephric space?
The perinephric space is a cone-shaped compartment within the abdomen containing the kidney, adrenal gland, perinephric fat, a type of connective tissue called fibrous bridging septa, and a network of blood vessels and lymphatic vessels. Perinephric abscesses form between the renal capsule of the kidneys and the Gerota’s fascia, within the perinephric space.
What causes a perinephric abscess?
Most perinephric abscesses are caused by complications due to either a urinary tract infection or due to infections that occur in the kidneys, bladder, ureters, or urethra. Urologic infections, such as urinary tract infections and sexually transmitted infections, can be carried through the blood to the kidneys causing pyelonephritis, which refers to inflammation of the kidney due to bacterial infection. If pyelonephritis is chronic or recurring, this can lead to a collection of infected material and consequent cell death (necrosis) in the perinephric space, forming a perinephric abscess. Other causes may include trauma and infection spreading from other body organs including the liver, cervix, pancreas, gallbladder, and appendix.
Certain medical conditions can predispose individuals to perinephric abscesses. These include diabetes mellitus, pregnancy, urinary tract infection, and structural abnormalities in the urinary tract. Additionally, many individuals with a perinephric abscess have associated kidney stones, which can block the flow of urine and allow bacteria to accumulate in the perinephric space.Risk factors that might worsen outcomes include advanced age, diabetes mellitus, and renal insufficiency (poor kidney function).
What are the signs and symptoms of a perinephric abscess?
The severity of symptoms depends on the extent of the infection and the comorbidities of the individual. Individuals with perinephric abscesses commonly present with fever, chills, flank pain, abdominal pain, and fatigue. The bacterial infection may travel to the groin or leg area, as well as to the right upper abdomen, where the liver is located, causing pain in those respective locations. If the lungs are affected, this may also lead to pain in the chest. Tenderness of the costovertebral area, located in the back at the bottom of the ribcage, is also common. Inflammatory skin changes are sometimes present, and less commonly, dysuria or pain and discomfort with urination may occur.
How is a perinephric abscess diagnosed?
Diagnosis of a perinephric abscess typically requires a review of medical history and a physical examination. An individual's medical history can reveal the presence of an associated infection that may have caused the abscess. During physical examination, individuals may present with a palpable mass. If an abscess is suspected, lab tests, including blood work and urine tests (urinalysis), are typically conducted to assess the presence of infection. In order to identify the abscess and define its extent, computed tomography (CT) scans are often used. CT scans can also help determine the presence of any radiological abnormalities that may be indicative of an abscess. In some cases, ultrasonography can also be used to identify the presence of an abscess.
How is a perinephric abscess treated?
The first line of treatment for perinephric abscesses is a course of antibiotics for at least two to three weeks. In some cases, percutaneous catheter drainage may also be necessary in order to drain abscess fluid. Percutaneous catheter drainage utilizes imaging guidance (CT and ultrasound) to place a thin needle through the skin and into the perinephric abscess to first obtain a sample of the infected fluid. Then, a drainage catheter is left in place to drain the abscess fluid, which can take up to several days. If antibiotic medication and drainage do not successfully treat the abscess, urologic surgery may be required.
Response to treatment may be monitored through assessment of clinical symptoms, such as presence of low back pain and temperature. The symptoms and associated infections should improve with successful treatment.
Do you drain a perinephric abscess?
Perinephric abscesses may be drained depending on the size of the infected area. A perinephric abscess larger than 3 cm (1.18 inches) is more likely to be drained, while an abscess smaller than 3 cm (1.18 inches) may initially be treated with an antibiotic. Drainage may also be performed if symptoms and radiological abnormalities persist after several days of appropriate antibiotic treatment.
What are the most important facts to know about perinephric abscesses?
Perinephric abscess refers to the accumulation of infected material and consequent necrosis of tissues within the perinephric space, surrounding the kidneys. It can result from complications of pyelonephritis or it can be due to spread of infection from other body organs through the bloodstream. The perinephric abscess forms between the renal capsule, which directly lines the kidneys, and the Gerota’s fascia encapsulating the fat layer. Symptoms commonly include flank pain, fever, and chills. Medical history review, physical examination, and laboratory testing can indicate the presence of an abscess and an associated infection. CT scanning can then be used for further diagnosis and treatment of a perinephric abscess. The first line of treatment includes antibiotic therapy followed by percutaneous catheter drainage if necessary. Surgery may also be required if these treatments are not effective.
Clinical Reasoning: Urinary tract infections
High Yield: Urinary tract infections
Resources for research and reference
Aizenstein, R. I., Owens, C., Sabnis, S., Wilbur, A. C., Hibbeln, J. F., & O'Neil, H. K. (1997). The perinephric space and renal fascia: review of normal anatomy, pathology, and pathways of disease spread. Critical Reviews in Diagnostic Imaging, 38(4): 325-67. Retrieved December 2, 2020, from https://pubmed.ncbi.nlm.nih.gov/9376088/
Kidneys. (n.d.). In NIH: National Cancer Institute SEER Training Modules. Retrieved November 3, 2020, from https://training.seer.cancer.gov/anatomy/urinary/components/kidney.html
Okafor, C. N. & Onyeaso, E. E. (2020). Perinephric Abscess. In StatPearls [Internet]. Retrieved December, 3, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK536936/
Percutaneous Abscess Drainage. (n.d.). In RadiologyInfo.org. Retrieved November 4, 2020, from https://www.radiologyinfo.org/en/info.cfm?pg=percabscessdrn
Yu, A. S., Chertow, G. M., Luyckx, V. A., Marsden, P. A., Skorecki, K., & Taal, M. W. (2020). Brenner and Rector’s The Kidney (11 edition). Philadelphia: Elsevier.