Abdominal Emergencies in Bariatric Patients

Key Points

• Bariatric surgical interventions require a multidisciplinary approach preoperatively and postoperatively.

• Fluoroscopy, abdominal ultrasound, and computed tomography are the most commonly utilized imaging modalities in assessing these patients.

• There are a number of common and uncommon complications (e.g., leaks, collections, bowel obstructions, internal hernias) associated with these procedures that the radiologist should be familiar with in order to help guide clinical and surgical management.

• A high index of suspicion and a low threshold for imaging are important for prompt detection of internal hernias.

Introduction

Obesity is a disease of increasing global prevalence. It has detrimental effects on individual health as well as on health care systems. In addition to lifestyle changes and medical management, several surgical procedures have been developed over the years to treat a subset of obese patients. Some of the more well-known procedures are Roux-en-Y gastric bypass (RYGB) and laparoscopic adjustable gastric banding (LAGB). Other common surgical procedures include vertical banded gastroplasty (VBG), duodenal switch, and sleeve gastrectomy. As with any surgical intervention, there is potential morbidity and mortality associated with these procedures. The radiologist plays an essential role in identifying and diagnosing the common and uncommon complications and can directly influence the management of these cases. Modalities such as fluoroscopy and computed tomography (CT) are most commonly used for investigating these suspected complications. This chapter will review and discuss the imaging findings of common and uncommon complications of some of the more widely utilized bariatric surgical procedures.

Presurgical Imaging and Workup

Bariatric operations require a multidisciplinary approach that includes surgical, medical, psychological, nursing, and radiology teams, both preoperatively and postoperatively. Comprehensive preoperative assessment and planning are required prior to any bariatric operation, including a psychological, social, medical, and anesthetic assessment. These are beyond the scope of this chapter. However, some centers also perform preoperative radiological assessment, which includes ultrasound of the abdomen to assess for, among other things, the presence of gallstones and kidney stones, as well as to measure the abdominal wall thickness. In some instances, surgeons may perform an elective cholecystectomy at the same time as certain bariatric procedures, namely RYGB, as these patients have a higher incidence of cholecystitis due to altered anatomy and therefore altered absorption. Measurement of abdominal wall thickness is not a standard requirement but may assist the surgeons in choosing the appropriate laparoscopic equipment for each individual patient. This includes measuring the abdominal wall thickness from the skin surface to the ventral abdominal wall at the usual sites of laparoscopic ports, which are typically in the bilateral upper quadrants of the abdomen and in the supraumbilical region. Ultrasound could also be used to measure the left lobe of the liver, which could predict bariatric surgery difficulty.

Types of Commonly Performed Surgeries

The two main surgical approaches that have been adopted for achieving weight loss are restrictive procedures and bypass or malabsorptive procedures. The third category that has also gained popularity includes procedures with both restrictive and malabsorptive effects, such as the RYGB surgery. Many of these surgeries are now performed laparoscopically, which has been proven to decrease recovery time and reduce the complications associated with open surgical techniques.

Some examples of restrictive procedures include LAGB, VBG, and sleeve gastrectomy. Each of these different techniques has been successful in achieving their goal, and each carries its own set of associated complications, some of which overlap. Examples of malabsorptive or bypass procedures include RYGB and biliopancreatic diversion gastric bypass (BPD). Interventions offering both restrictive and malabsorptive effects include RYGB, LAGB, and sleeve gastrectomy.

Imaging Modalities and Protocols

The evaluation of bariatric surgical complications depends on multiple factors. The modalities that may be used include abdominal radiographs, upper gastrointestinal (GI) fluoroscopic studies, and CT imaging. Their utilization and applications are dictated by the clinical presentation. For instance, abdominal radiographs may be used for the initial evaluation of suspected bowel obstruction or to detect intraabdominal free air.

The fluoroscopic study is often a single-contrast study limited to evaluating for major complications. It can be helpful to assess for leaks or strictures, although the reliability and accuracy depend on the technique used and the radiologist’s expertise.

CT is much more valuable, as it offers a detailed anatomic assessment, allows for characterization of any postprocedure complications, and allows for the detection of any alternative pathologies aside from bariatric surgery complications. The CT protocol should include both intravenous and oral contrast administration to accurately assess the anatomy and complications. The images are acquired in the portal venous phase (~70 seconds post–intravenous contrast administration). As well, administration of a small amount of positive oral contrast (~150 mL) is useful to evaluate for proximal leaks and to better delineate the anatomy. Images are then reconstructed in the coronal and sagittal planes, which is helpful in providing perspective on the anatomy as well as evaluating mesenteric and vascular distortion, especially in cases of RYGB.

In the unique case of suspected bariatric surgery complications in pregnant patients, such as post-RYGB internal hernia, abdominal magnetic resonance imaging (MRI) has been shown to be a safe and a valuable imaging technique. MRI has specificity that is comparable to CT for diagnosing post-RYGB internal hernias, and its sensitivity approaches that of CT.

Finally, the role of routine imaging following bariatric surgery is variable, and there are no consensus guidelines as to whether any routine imaging should be performed. For certain procedures, especially procedures with stapling or anastomosis, surgeons may elect to assess for any leak in the early postoperative period with an upper GI fluoroscopic study. ^16,19

General Complications

As with all surgical procedures, some patients can experience one of a number of possible complications. Certain complications are similar to other surgical procedures, such as bleeding, infection, and wound-related complications, including dehiscence, delayed healing, hematoma, or fluid collections. Several complications have been noted to arise in relation to the different bariatric procedures commonly performed, some are common in every procedure, and a few complications are unusual or are seen more often in certain bariatric surgical procedures than others. ^{, ,}

Collections

These can be seen with any of the bariatric surgical interventions. They could be secondary to anastomotic leak with or without superimposed infection. CT is the modality of choice to assess for the presence of the different types of collections, including contained leaks and abscesses. Additionally, a hematoma is an important postoperative complication and may occur with RYGB, duodenal switch, or sleeve gastrectomy ( Fig. 8.1 ). High-density fluid collections (60–80 HU) point to a hematoma. A CT will also allow for the identification of active contrast extravasation in cases of ongoing active bleeding. Therefore, if there is a high index of suspicious for a hematoma and/or active hemorrhage, a multiphasic CT study could be performed to allow for the identification of active contrast extravasation.

Bowel Obstruction

Bowel obstruction is a common postsurgical complication and is most commonly seen secondary to adhesions ( Fig. 8.2 ). This may be detected after any of the aforementioned bariatric surgical procedures. In patients who have undergone RYGB or duodenal switch, care must be taken to exclude an internal hernia as the cause of obstruction, as it may have important consequences and unique management. Internal hernias will be further discussed below. Strictures are also a common cause of obstruction and should be considered. CT examination is the modality of choice to evaluate for suspected obstruction.

Suture Dehiscence or Leak

These usually occur along the suture lines, such as in sleeve gastrectomy, or at the sites of anastomosis, particularly in procedures such as duodenal switch and RYGB. Suture dehiscence appears as focal interruption of the staple line and is readily evaluated by CT with or without oral contrast. Anastomotic leaks are best assessed with oral contrast, whether through an upper GI fluoroscopic assessment or CT ( Fig. 8.3 ). The latter is helpful in identifying further complications that may or may not be related directly to leaks such as hematomas and abscesses.

Surgical Procedures and Associated Complications

Band Slippage

Band slippage occurs when the gastric band is dislocated or has migrated from its original position. This results in herniation of parts of the stomach through the gastric band, causing eccentric dilatation of the pouch and band malposition. The two observed types that can occur are anterior and posterior band slippage. Anterior band slippage occurs due to instability of the fixation sutures and result in herniation of the superior and anterior portions of the stomach and a clockwise rotation of the gastric band. Posterior slippage is usually seen in patients with retrogastric band placement, a technique that is no longer performed. This results in herniation of the inferior and posterior portions of the stomach and counterclockwise rotation of the gastric band.

An abdominal radiograph can confirm the diagnosis if there is evidence of an abnormal configuration of the gastric band, usually resulting in an abnormal “O-shaped” configuration (the “O” sign), as opposed to its normal rectangular appearance ( Fig. 8.4 ). An upper GI study can support the diagnosis with minimal or decreased passage of contrast through the gastric band, as well as eccentric dilation of the gastric pouch. Complications that can result from band slippage include ischemia and necrosis of the gastric pouch.