Perinephric Abscess - Causes and Clinical Management

What Is an Abscess?

An abscess is a mass formed due to pus build-up after a bacterial infection. It can occur anywhere in the body, and there are mainly two types of abscesses, including cutaneous abscesses and internal abscesses. As the name suggests, the skin abscess usually develops below the skin, whereas internal abscesses develop in the internal organs or the interstitial spaces. The majority of abscesses are caused by infections and can be easily palpated (felt). They are painful and warm to the touch and are most commonly seen on the skin of the armpits, around the vagina, anus, back of the spine, groin, and around the tooth. Abscesses that occur due to inflammation or blockage of the hair follicles are known as carbuncles. Abscesses can be treated by antibiotics or are drained surgically.

What Is a Perinephric Space?

A perinephric space is a cone-shaped area behind the peritoneum (abdomen) and consists of the kidneys, adrenal gland, perinephric fat, and connective tissue known as the fibrous bridging septa. Adrenal glands are present above the kidneys and carry out the body's endocrine functions. The blood vessels and lymph nodes supplying the perirenal space are also present in the perinephric space. The disorders related to the perinephric space might originate from within or outside the perinephric fascia. Sometimes, the diseases might arise from the kidneys or adrenal glands and involve the perinephric space. It is important to treat the conditions affecting the perinephric space because it contains vital urinary tract structures.

What Is a Perinephric Abscess?

A perinephric abscess resembles a pus pocket and is one of the most common complications of urologic infections. Earlier, it was believed that perinephric abscesses occur due to prolonged bacteremia (bacterial infection), but now it has been discovered that perinephric abscess occurs due to urologic infections. A pair of kidneys are located beneath the rib cage and are covered by a thin layer of tissue known as the renal capsule. Within the perinephric space, a layer of perinephric fat protects the kidneys from getting damaged. A layer of connective tissue known as the renal fascia is present in this perinephric fat layer. The anterior portion of the renal fascia is known as Gerota’s fascia. A perinephric abscess mainly affects the capsule surrounding the kidneys and Gerota’s fascia.

What Are the Causes of a Perinephric Abscess?

A perinephric abscess might occur due to a urologic infection or when the infection spreads into the perinephric space from the kidneys via the bloodstream. In addition, these abscesses might occur due to the spread of bacteria from urinary tract infections or sexually transmitted diseases. Pyelonephritis is a life-threatening condition that affects the kidneys and might be one of the reasons for perinephric abscess. If the patient suffers from pyelonephritis repeatedly, the infected materials accumulate in the cells of the perinephric space and give rise to an abscess. Other causes of perinephric infections include trauma and bacteria from the organs like the liver, gallbladder, pancreas, cervix, and appendix. People suffering from Crohn’s disease and inflammatory bowel disease are more likely to develop a perinephric abscess. In addition, the layer of fat present in the perinephric space might get infected by Staphylococcus aureus. The factors that increase the risk of a perinephric abscess include aging, diabetes, renal insufficiency, and vertebral osteomyelitis (a serious bone infection). The disease might also be present congenitally due to disturbance in the development of the urinary tract.

What Are the Signs and Symptoms of a Perinephric Abscess?

The symptoms depend on the severity of the condition and other diseases the patient is suffering from. The signs and symptoms of perinephric abscess are listed below:

• Fever, chills, nausea, and vomiting.

• Flank pain and tiredness.

• Abdominal pain.

• Pain might occur in the groin due to the migration of bacteria.

• If the bacteria infects the lungs, chest pain is usually noted.

• Costovertebral angle tenderness.

• Inflammation of the skin.

• Dysuria (painful urine).

• Difficulty in passing urine.

How to Evaluate the Case of a Perinephric Abscess?

Perinephric abscess is a serious condition, and delayed diagnosis is usually the reason behind increased death rates. A thorough clinical examination and a medical history are required to diagnose a perinephric abscess. Then, the laboratory tests and imaging tests can be done to confirm the diagnosis:

• Medical History - A thorough medical history of the patient must be taken to evaluate the condition. The doctor might ask about the medical history verbally or in the form of questionnaires. Usually, patients presenting with fever for four to five days even after completing the antibiotic course for pyelonephritis are suspected to be at a higher risk of developing a perinephric abscess.

• Physical Examination - The physical examination is done to check the signs of a perinephric abscess. A palpable mass in the abdomen and tenderness in the area between the spin and the 12th rib (costovertebral angle) is indicative of a perinephric abscess.

• Blood Test - A blood test is done to check the entire blood profile of the patient. It is a simple procedure wherein a needle is injected into the patient’s arm to draw a small amount of blood. The blood sample is then examined in the laboratory under a microscope. Patients suffering from perinephric abscesses show elevated leukocyte counts, raised erythrocyte sedimentation rate (ESR), and raised C-reactive protein levels.

• Urinalysis - Urinalysis or urine sample test is a procedure where the patient collects his urine in a container and sends it to the laboratory. This test is specifically done to check proteinuria (the presence of proteins in the urine), bacteria, and white blood cells. If a perinephric abscess spreads into the bloodstream, bacteria can be seen in the urine.

• Computed Tomography (CT) Scan - It is one of the most common imaging methods used to diagnose urinary tract disorders. During this imaging test, the patient lies on a padded table that slides into a cylinder or a tunnel-shaped device where the X-rays are taken. CT scan provides three-dimensional images of the urinary tract and the areas surrounding the kidneys. Therefore, it can be used to diagnose perinephric abscesses and other anomalies.

• Ultrasound - In this imaging procedure, the patient lies on the padded table, and the doctor moves a device, also called the transducer over the abdomen. The sound waves reach the body with the help of a transducer, and images are obtained on the computer screen. Hence, the doctor can detect the abnormalities present in the perinephric space.

How Is Perinephric Abscess Managed?

Antibiotics are the first line of treatment for perinephric abscesses because they directly target the disease-causing bacteria. Empiric antibiotics must be administered to the patient as they kill the Staphylococcus bacteria. The choice of antibiotics depends upon the suspected organism. However, the doctor might delay the empiric antibiotic therapy if the patient is stable and the abscess drainage can be done immediately. The antibiotics must be administered for two to three weeks. The following drugs are usually administered in patients suffering from perinephric abscesses:

• Nafcillin.

• Cefazolin.

• Gentamicin.

• Ceftazidime.

• Ampicillin.

• Mezlocillin.

• Ethambutol.

• Isoniazid.

• Rifampin.

How Is the Perinephric Abscess Drained?

A perinephric abscess can be drained with the help of a percutaneous catheter. A catheter is a tube inserted into the body to facilitate urine drainage or pus drainage. The decision to drain the abscess depends upon its size. If the abscess is greater than 3 centimeters, it is usually treated with antibiotics. However, abscesses larger than 3 centimeters are drained by a catheter. During the drainage procedure, the abscess is first located by a CT scan or an ultrasound, and a needle is inserted at the site along with the catheter. It is allowed to remain there for a few days to facilitate pus drainage. Once the doctor is assured that the pus has been drained from the abscess, the drainage needle is removed. Finally, the patient is asked to continue the antibiotics for a few days until the infection subsides completely.

What Are the Complications of a Perinephric Abscess?

The perinephric abscess can cause severe complications because of the spread of bacteria to the surrounding organs. The complications of perinephric abscess are listed below:

• Excessive bleeding in the perinephric space.

• Abscess in the sides (flank abscess).

• Empyema (pus pocket inside the body cavity).

• Subphrenic abscess (collection of infected material near the lungs).

• Pneumonia (a lung disease that occurs when the infection spreads to the lungs).

• Atelectasis (complete or partial lung collapse).

• Sepsis.

• Peritoneal rupture.

Conclusion:

A perinephric abscess occurs when the infected fluid gets collected in the perinephric region. It is an uncommon condition and can affect both males and females. The signs and symptoms of perinephric abscess are similar to many other urologic conditions. Therefore, it is challenging for doctors to identify it. However, laboratory tests and imaging tests help confirm the diagnosis. The patient need not worry as the perinephric abscess is not a life-threatening condition, and there is a fixed treatment plan. However, surgical intervention or abscess drainage is required in rare conditions when the abscess is more than 3 centimeters in dimension. Hence, the patient must consult the urologist to know more about the treatment of a perinephric abscess to prevent complications and improve the condition.