Absess Intraperitoneal

Clinical Some abscesses develop spontaneously, although most are secondary to postoperative complications or spread from a source in an adjacent structure, such as diverticular disease, appendicitis, cholecystitis, and so on. Fluid collections communicating with bowel can become huge, and patients have few symptoms due to the internal drainage. At times an abscess and peritonitis coexist, and the initial inciting event is difficult to identify. gallstone falling into the peritoneal cavity during laparoscopic cholecystectomy may not be readily retrievable. Although many of these intraperitoneal gallstones are innocuous, they do serve as a potential nidus for abscess formation, with some of these abscesses manifesting years later. An occasional dropped appendicolith, occurring mostly during laparoscopic appendectomy, results in a similar finding. At times the specific etiology for such an abscess is uggested by CT or US.

This is radiology images of the Postoperative abscess extending from the left hemidiaphragm inferiorly into left lower quadrant (arrows), communicating with the stomach. Barium sulfate was the contrast material used; it does not affect abscess healing.

Imaging
                   Computed tomography, US, MRI, or scintigraphy should detect and localize most intraabdominal abscesses, and most can then be drained percutaneously, generally under US guidance. Numerous comparison studies have shown CT and US accuracies of over 90% in detecting intraabdominal abscesses. Whether the greater resolution of CT or the greater portability of US determine the modality used, clinically the availability is the deciding factor. A note about subphrenic abscesses. It is almost unheard of to have a subphrenic abscess without an associated pleural effusion. Even a chest radiograph should detect such an effusion, and the absence of effusion essentially excludes a subphrenic abscess. If imaging identifies a suspicious abscess beneath the right hemidiaphragm but no pleural effusion is detected, an intrahepatic rather than a subphrenic abscess is more likely. Gas in a fluid collection generally implies an abscess,but gas bubbles are also seen in retained surgical sponges even without an abscess. Large amounts of gas suggest bowel communication, a finding seen with other benign and malignant conditions.
                   Computed tomography of a typical abscess shows a fluid-filled structure surrounded by a contrast-enhancing rim. Such a finding is not limited to abscesses and is also seen with some necrotic tumors and other benign conditions such as a hematoma and various cystic structures. Also, not all abscesses have this appearance. Differentiation of an abscess and a benign fluid collection is difficult, especially if the wall is thick. Loculated fluid after abdominal surgery tends to develop primarily in the abdomen and after pelvic surgery loculated fluid is mostly in the pelvis, but this is of limited use in differentiating benign fluid from an abscess.
                  Abscesses are hypointense on T1- and hyperintense on T2-weighted MR images; about half are homogeneous in appearance. Gadoliniumenhanced T1-weighted fat-suppressed images identify abscesses as fluid collections surrounded by a contrast-enhancing rim. Gas within an abscess appears as a signal void on both T1- and T2-weighted images. Coronal and sagittal reconstruction aids in differentiating an abscess from bowel. Fluid layering occurs in some abscesses, with hypointense material, presumably representing protein, being dependent on T2-weighted images, and such a finding in the peritoneal cavity is strong presumptive evidence of an abscess. Overall, MR sensitivity in detecting abscesses is close to 100%. Scintigraphy detects most abdominal abscesses. Useful radiopharmaceuticals include gallium-67 citrate, indium-111 leukocytes, and Tc-99m leukocytes. A major limitation of Ga-67 citrate scintigraphy is the prolonged time required to perform the study.

Radiology images of the Left subphrenic abscess secondary to a perforated gastric fundal adenocarcinoma.The entire fundus is amputated by tumor and abscess (arrows). The study was performed primarily for unexplained weight loss.

Therapy
                   Percutaneous abdominal abscess drainage is an established technique, and almost all welldefined unilocular abscesses can be successfully drained. A majority of abscesses are cured with initial drainage. Recurrent abscesses can be drained percutaneously in most patients and surgery avoided in about half. Complex abscesses consisting of loculated, poorly confined, or multiple abscesses or those associated with a fistula have a lower success rate and often require several drains. A single abscess is often drained using US guidance, but multiple abscesses are easier to drain with CT guidance.
                  Distinguishing an abscess from necrotic tissue can be difficult. At times aspirate cytology is helpful. Similar to surgical drainage, attempts to drain infected necrotic tumors percutaneously are rarely successful. Conversion to surgical drainage (and often associated resection) is required with the presence of unhealing abscesses or fistulas and bowel or pancreatic necrosis. Catheter-induced bleeding is an occasional complication requiring surgical correction.

               Crohn’s disease abscesses can be drained percutaneously using image guidance, and the patient is thus stabilized. These abscesses tend not to resolve completely, especially if they involve an enteric fistula. Some left subphrenic abscesses cannot be readily drained using a transabdominal approach, and a transpleural approach is necessary. At times a drainage catheter is inserted through the pleura. Regardless of catheter position, most abscesses are successfully drained, although a transpleural approach risks a pneumothorax, requiring its own therapy. Abscess drainage using a transrectal or transvaginal approach with a combination of endoluminal US and fluoroscopy for needle advancement, tract dilation, and catheter insertion, combined with appropriate antibiotics, is effective therapy for most pelvic abscesses. Patients undergoing transrectal aspiration or drainage have less procedure-related pain and catheter pain than those with a transvaginal approach. A viable option for some pelvic abscesses is US-guided transperineal catheter drainage.
                Pelvic abscesses are readily drained in children and adolescents. The average hospital stay for children after image-guided transrectal drainage of pelvic abscesses tends to be shorter than after open surgical drainage. Surgical drainage is associated with more complications than percutaneous drainage, but comparison studies often have a built-in bias against surgery—patients undergoing surgical drainage tend to be sicker.
Computed tomography–guided transgluteal percutaneous drainage of deep pelvic abscesses through the greater sciatic foramen is an option in both adults and children. A majority of vancomycin-resistant enterococcal abscesses can be drained percutaneously, although the rate of successful therapy is lower than with more conventional abscesses; at times drainage provides a first clue to the presence of vancomycin-resistant enterococci.

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