Abdominal Emergencies in Cancer and Immunocompromised Patients

Introduction

Oncology and immunocompromised patients pose a unique challenge when presenting with abdominal pain in the emergency department. History and physical exam findings can be misleading due to pain medication or a blunted inflammatory response. In addition to the more common acute pathologies seen in otherwise healthy patients, cancer and immunocompromised patients can present with abdominal pain directly due to an underlying malignancy, a malignancy-related complication, a complication of immunosuppression, or a treatment-related complication. In this chapter, an approach to these patients is discussed, and acute processes related to a variety of organ systems are reviewed. A comprehensive discussion of treatment-related complications is provided, followed by a review of imaging pitfalls.

Approach to Cancer and Immunocompromised Patients With Abdominal Pain

Acute abdominal pain is one of the most common complaints of oncology patients presenting to the emergency department, with the gastrointestinal system being the most frequent source. Identifying the cause of pain can be challenging, as the clinical presentation may be misleading. While it is possible that pain may be due to uncontrollable cancer progression, all reasonable attempts must be made to ensure there are no reversible sources of pain that are treatable and that, once treated, may improve quality of life.

Contrast-enhanced abdomen and pelvis computed tomography (CT) is usually appropriate for immunocompromised patients with acute nonlocalized abdominal pain, and is a favored initial imaging strategy compared with radiographs, ultrasound, or magnetic resonance imaging (MRI) by the American College of Radiology. Bowel pathologies including obstruction and enterocolitis are common in this population; neutropenic enterocolitis (typhlitis) is the most common cause of pain in neutropenic cancer patients ( Fig. 5.1 ). Other infectious and inflammatory processes of the bowel include opportunistic infections such as Clostridium difficile colitis ( Fig. 5.2 ), cytomegalovirus colitis, and treatment-related conditions such as graft-versus-host disease ( Fig. 5.3 ). CT plays an important role in both establishing these diagnoses and excluding other causes of pain. Early initiation of medical treatment may preclude the need for an operation. The threshold to perform CT should therefore be lower for these patients than for the general population. This is particularly true for those with terminal malignancies; cumulative ionizing radiation exposure is unlikely to have any meaningful implication for these patients.

Abdominal radiographs play a limited role in the workup of abdominal pain in the emergency department. Sensitivity of radiographs for the diagnosis of enterocolitis and other acute abdominal pathologies is low, with the majority of radiographs not contributing to management, as shown by Kellow et al. Even more concerning is that, in their study, the majority of patients who had follow-up abdominal imaging after initial normal radiographs were found to have an abnormality, suggesting that abdominal radiographs miss a considerable number of pathologies.

Similar to radiography, ultrasound has a limited role in cancer and immunocompromised patients with generalized abdominal pain. Ultrasound can be useful in the setting of localized pain, particularly if the presentation is suggestive of acute cholecystitis, as there is limited evidence for the utility of CT for this diagnosis. Ultrasound can also be used for dynamic assessment of the abdomen, for example when assessing abdominal wall hernias, including at prior surgical incision sites or for an adynamic ileus. Another advantage of ultrasound is the lack of ionizing radiation, which is relevant for younger immunocompromised patients without terminal conditions who are likely to experience recurring abdominal pain. Patients with inflammatory bowel disease fit this profile. Ultrasound of the bowel is a highly effective but infrequently utilized tool for patients with Crohn disease and acute abdominal pain. Familiarity with gut signature and the patterns of inflammatory bowel disease seen on ultrasound is recommended for all radiologists involved in the care of emergency department patients.

MRI is not generally performed as an initial imaging technique for patients with acute abdominal pain, with a few exceptions. MRI is accurate for the diagnosis of appendicitis in pregnant patients ( Fig. 5.4 ). Magnetic resonance cholangiopancreatography can be useful for assessment of the biliary system for obstruction or for iatrogenic biliary leaks (using hepatobiliary-specific contrast agent), which may be relevant for patients with prior hepatobiliary interventions where this is a concern.

Radiologists should have a low threshold to image the abdomen and pelvis in cancer and immunocompromised patients, and for most cases CT is a pragmatic starting point. In the next section, vascular complications are explored.

Vascular Complications

Abdominal malignancies can cause multiple vascular complications from advanced disease stage that can complicate surgical planning and often portend a worse prognosis. Complications include intratumoral hemorrhage, as is commonly seen with large and vascular tumors, bland thrombus formation from a hypercoagulable state, and also direct tumor vascular invasion, which can lead to vascular occlusion. Vascular complications can also arise secondary to interventions and treatment, especially with antiangiogenic chemotherapeutic agents.

Abdominal malignancies such as hepatocellular carcinoma (HCC), pancreatic adenocarcinoma, and renal cell carcinoma (RCC) have a propensity to invade and occlude vessels. The inferior vena cava (IVC), portal, splanchnic, and pelvic veins are often involved. Vascular occlusion can be secondary to direct tumor invasion (tumor in vein) or secondary to bland thrombus. Although it can be difficult to distinguish tumor from bland thrombus on imaging, vessel expansion, enhancement/arterial flow within the filling defect, contiguity and morphological resemblance to the primary mass, intermediate T2 signal, and diffusion-weighted imaging hyperintensity on MRI favors tumor in vein rather than bland thrombus ( Fig. 5.5 ). Vascular invasion is usually a gradual process allowing for collateral formation; however, rarely, vascular invasion by tumor can cause acute pain or organ infarction secondary to extensive thrombosis or even embolization. Hepatic infarction secondary to tumor in vein is rare given dual hepatic blood supply. However, involvement of the hepatic veins or IVC by hepatic, renal, or adrenal malignancies, or metastatic retroperitoneal lymphadenopathy or primary vascular malignancies, can cause acute Budd-Chiari syndrome. In acute Budd-Chiari syndrome, the only findings on imaging may be hepatic venous occlusion and ascites. On contrast-enhanced imaging, there can be patchy decreased enhancement in the peripheral portions of the liver with sparing of the central portion due to its direct venous drainage into the IVC. Pancreatic adenocarcinoma is notorious for vascular invasion, but due to its extensive collateral blood supply pancreatic necrosis secondary to vascular occlusion is rare. Nevertheless, involvement of the splanchnic and splenic veins can cause acute mesenteric ischemia and splenic infarction, respectively. Acute bowel ischemia can be identified by circumferential bowel wall thickening with either mural hypoattenuation due to submucosal edema/inflammation or mural hyperattenuation from hemorrhage, and decreased enhancement on postcontrast images. Pneumatosis suggests infarction, which may warrant urgent surgical resection. The spleen is particularly susceptible to acute infarction due to its rich vascularity and exclusive supply by the solitary splenic artery. Splenic infarction can present with acute left upper quadrant pain and is seen on CT as wedge-shaped peripheral hypodensities or diffuse hypoattenuation in severe cases ( Fig. 5.6 ).

Tumor-associated hemorrhage is an important cause of spontaneous hemoperitoneum, commonly seen with hypervascular neoplasms such as HCC, hepatic adenoma, RCC, adrenal pheochromocytoma, adrenocortical carcinoma, and hepatic metastases from melanoma. HCC is one of the most common causes of spontaneous nontraumatic hemorrhage, with higher incidence in patients with chronic hepatitis B viral infection and those with cirrhosis. HCC rupture carries a poor prognosis, with an overall mortality rate of 24% despite advancements in endovascular treatment. Subcapsular tumors are more prone to hemorrhage, while intraparenchymal tumors can present with acute pain secondary to the tamponade effect of normal adjacent liver parenchyma without significant blood loss. Spontaneous renal and perirenal hemorrhage, also known as Wunderlich syndrome, is reported in 0.3% to 1.4% of RCCs, most commonly the clear cell subtype. Other tumors known to bleed spontaneously include gastrointestinal stromal tumors (GISTs), hepatic angiosarcomas, and hepatic metastases from lung cancer. Abdominal tumor hemorrhage can also be iatrogenic from systemic anticoagulation and biopsy. A hyperdense area on noncontrast CT with extravascular contrast blush on the arterial phase that expands on the delayed phase is consistent with active extravasation, for which urgent embolization or surgical management may be needed. The presence of a high-attenuation hematoma abutting an organ can be used to identify the site of hemorrhage and is known as the sentinel clot sign . An underlying tumor must be ruled out in all cases presenting with spontaneous nontraumatic hemorrhage, either on follow-up imaging or using subtraction postcontrast MRI ( Fig. 5.7 ).

Tumor and Organ-Specific Complications

Many abdominal malignancies can exert mass effect or invade and obstruct organ systems including the biliary system, urinary system, gastrointestinal tract, vessels, and neurological structures including the spinal cord. Obstruction or compression of these structures can lead to devastating consequences, for example, biliary sepsis, renal failure, bowel obstruction, thrombosis, and paralysis. In addition, all can be associated with debilitating pain. Recognition of these pathologies is critical, as they may be amenable to intervention that can substantially improve quality of life.

Hepatobiliary System

Obstruction of the biliary system may result from an intraluminal mass, adjacent tumor mass effect, or invasion. Obstruction may also occur at the extrahepatic or intrahepatic level, such as from pancreatic adenocarcinoma, cholangiocarcinoma, ampullary and periampullary tumors, and also HCC and metastases ( Fig. 5.8 ). Biliary obstruction results in bile stasis and accumulation, which leads to jaundice, hepatic dysfunction, and acute liver failure. Prolonged stasis can act as a nidus for infection, causing cholangitis, hepatic abscess, and sepsis. Obstruction of the common bile duct is typically treated by placement of a biliary stent, usually a removable plastic stent if the obstructing tumor may respond to chemotherapy or radiotherapy. Otherwise, a metallic stent can be considered if survival is expected to be greater than 4 months, as these have better long-term patency. Stents are an option when the biliary system is obstructed at one site; however, multifocal hepatic tumors obstructing multiple separate intrahepatic bile ducts may not be amenable to treatment. Occasionally, more than one percutaneous stent may be inserted, or a combination of stenting and percutaneous drainage may be used, for example, to drain the largest portion of liver in an attempt to lower the serum bilirubin level to initiate chemotherapy for potentially resectable disease to optimize the future liver remnant, or for management of cholangitis or severe pruritis.

Acute pancreatitis is the presenting feature of pancreatic adenocarcinoma in up to 13% of cases and is often associated with a delayed diagnosis. Other, less common causes of acute pancreatitis in malignancy include metastases (especially from small cell lung cancer), malignant hypercalcemia, chemotherapy-induced pancreatitis (L-asparaginase, ifosfamide, paclitaxel, cisplatin, vinorelbine, cytarabine, tretinoin, sunitinib, and sorafenib), and pancreatitis associated with newer classes of antineoplastic therapies. On imaging, there can be pancreatic enlargement, peripancreatic fat stranding with or without collections, and pancreatic necrosis similar to other benign causes of pancreatitis. It is imperative to assess for underlying differential parenchymal enhancement and mass effect to rule out a malignant cause. Pancreatic ductal dilatation with a duct to parenchyma ratio of more than 0.34, double duct sign, vascular encasement, vessel deformity, and increased ratio of the superior mesenteric artery to the superior mesenteric vein all suggest an underlying pancreatic adenocarcinoma rather than mass-forming pancreatitis. Alternatively, the duct penetrating sign, characterized by smooth narrowing of the pancreatic duct traversing a mass, suggests an inflammatory mass. Smaller pancreatic lesions can be overlooked due to changes of acute pancreatitis and may only be seen on follow-up imaging.