Anatomical Overview
The transverse colon and its mesocolon divide the general peritoneal cavity into the supracolic and infracolic compartments. The supracolic compartment, also known as the subphrenic region, is further separated by the liver into the suprahepatic and subhepatic spaces. The suprahepatic space is divided by the falciform ligament of the liver into left and right compartments, while the subhepatic space is divided by the ligamentum teres hepatis (round ligament) into right and left subhepatic spaces. The left subhepatic space is further subdivided by the hepatogastric ligament and the stomach into the left anterior and posterior subhepatic spaces. The left posterior subhepatic space corresponds to the omental bursa (lesser sac). Due to the small size of the left lateral lobe of the liver, the left anterior subhepatic space and the left suprahepatic space are practically continuous, forming a unified left subphrenic space. Additionally, an extraperitoneal space exists between the layers of the coronary ligaments.
A subphrenic abscess refers to the accumulation of pus in one or both spaces between the diaphragm and the transverse colon or its mesocolon. Such abscesses may develop in one or more of these anatomical compartments.
Pathology
When patients lie supine, the subphrenic region represents the lowest position, leading to the accumulation of purulent fluid in this area during acute peritonitis. Bacteria may also reach the subphrenic space through the portal vein or lymphatic system. Approximately two-thirds of patients with acute peritonitis experience complete absorption of intra-abdominal purulent fluid following surgical or medical treatment, while about one-third of patients develop localized abscesses. The location of the abscess correlates with the primary disease. Duodenal ulcer perforations, suppurative infections of the gallbladder and bile ducts, and perforated appendicitis often result in abscesses in the right subphrenic space, while gastric perforations and infections following splenectomy are more likely to lead to abscesses in the left subphrenic space.
Small subphrenic abscesses may resolve through non-surgical treatment. Larger abscesses, due to prolonged infection, may exhaust the body and result in systemic debilitation. Subphrenic infections may cause reactive pleural effusion or spread to the pleural cavity through lymphatic pathways, leading to pleuritis or empyema. Erosion of the gastrointestinal wall by the abscess may result in recurrent gastrointestinal bleeding or the formation of internal fistulas (such as intestinal or gastric fistulas). Sepsis may occur in patients with compromised immune function.
Clinical Presentation
Once a subphrenic abscess develops, both systemic and local symptoms become evident.
Systemic Symptoms
Fever is often observed, initially presenting as remittent fever before progressing to persistent high fever once the abscess has formed, though moderate persistent fever may also occur. An accelerated heart rate, thick and greasy tongue coating, fatigue, weakness, night sweats, anorexia, and weight loss are common. The white blood cell count is typically elevated, with an increased proportion of neutrophils.
Local Symptoms
There is often constant dull pain at the site of the abscess, which intensifies with deep breathing. Pain is usually localized to the subcostal margin near the midline or below the xiphoid process. Diaphragmatic irritation from the abscess may cause hiccups. Subphrenic infections can lead to pleural and pulmonary reactions, including pleural effusion, segmental atelectasis, cough, and chest pain. Tenderness upon percussion in the hypochondrium is not uncommon. In severe cases, localized skin pitting edema and increased skin temperature may develop. Right subphrenic abscesses may enlarge the liver dullness on percussion, while diminished or absent breath sounds may be noted in the lower chest on the affected side. Patients who have received extensive antibiotic treatment may exhibit atypical local symptoms and signs.
Diagnosis and Differential Diagnosis
The development of fever and abdominal pain during the treatment of acute peritonitis, infections of intra-abdominal viscera, or a few days after abdominal surgery should raise suspicion for this condition. X-ray imaging may reveal pleural reactions, pleural effusion, or partial atelectasis of the lower lobe of the lung, along with evidence of a space-occupying opacity in the subphrenic region. Left subphrenic abscesses may cause displacement of the gastric fundus. Approximately 10–25% of abscess cavities contain gas, which may appear as a fluid-gas interface. Ultrasound or CT imaging offers significant diagnostic and differential diagnostic value for subphrenic abscesses. Ultrasound-guided aspiration not only aids in diagnosis but also allows for drainage, irrigation of the abscess cavity, and administration of effective antibiotics as part of the treatment. It should be noted, however, that negative aspiration results do not exclude the possibility of an abscess.
Treatment
In the past, subphrenic abscesses were primarily treated with surgical intervention. In recent years, percutaneous catheter drainage has shown favorable therapeutic outcomes. Supportive care is also crucial, including fluid replacement, blood transfusion, nutritional support, and the use of antibiotics.
Percutaneous Catheter Drainage
The advantages of this method include minimal invasiveness, the ability to perform it under local anesthesia, reduced likelihood of abdominal cavity contamination, and good drainage efficiency. Indications for this technique include localized unilocular abscesses close to the body wall. The procedure is typically carried out through collaboration between surgeons and ultrasound or radiology specialists. If the drainage attempt fails or complications arise, conversion to surgical intervention can be promptly undertaken.
Procedure
The puncture site, direction, and depth are determined based on the location of the abscess as visualized by ultrasound or CT scans. The site closest to the abscess with no intervening viscera is chosen. After identifying an appropriate puncture site, routine disinfection and draping are performed. Local anesthesia is administered, and under ultrasound guidance, a cannula needle is inserted into the abscess cavity. The needle core is removed, and approximately 5–10 ml of pus is aspirated for bacterial culture and antibiotic sensitivity testing. A guidewire is then introduced through the cannula, and the needle is withdrawn. The skin puncture site is enlarged using a scalpel. A dilator is used along the guidewire to widen the puncture tract, followed by the insertion of a relatively thick, multi-fenestrated catheter. The guidewire is then removed, and the catheter is secured. The abscess cavity can be routinely irrigated with sterile saline or antibiotic solutions. The catheter is removed once clinical symptoms resolve, ultrasound indicates significant reduction or disappearance of the abscess cavity, and daily pus output decreases to less than 10 ml. For small abscesses, complete aspiration followed by multiple washes with antibiotic solutions may suffice without catheter placement. Residual abscesses post-aspiration can be treated with repeated puncture and drainage if necessary. This approach has achieved a cure rate of approximately 80% for subphrenic abscesses and is now the primary method for treating this condition.
Incision and Drainage
This method is now rarely utilized. Preoperative ultrasound and CT imaging are used to confirm the abscess location, and the choice of incision depends on the specific site of the abscess. Subphrenic abscesses may be drained through various approaches, with a common choice being a subcostal incision through the anterior abdominal wall. This approach is suitable for abscesses located in the anterior regions of the right subphrenic space (e.g., above or below the right hepatic lobe) and the anterior left subphrenic space.