Oncologic Emergencies of the Abdomen and Pelvis

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Many of the more lethal malignancies originate from viscera in the abdomen and pelvis including tumors of the prostate, pancreas, liver, and colon/rectum.1 In the ongoing work to improve patient survival, imagers must be cognizant of oncologic emergencies. These are defined as acute, potentially life-threatening events that develop as effects of cancer or its treatment. The most common oncologic emergencies relate to the gastrointestinal system and have a high association with mortality.2,3 Oncologic emergencies can occur at any point during disease and may be the initial presenting manifestation. These emergencies are not limited to malignancies, as pathologically benign tumors may also present emergently causing life-threatening bowel, biliary, or ureteral obstruction.4 The imager’s role is critical as prompt diagnosis increases the likelihood of a positive outcome.

The imaging manifestations of oncologic emergencies can be categorized into distinct patterns affecting the vascular, biliary, bowel, and genitourinary systems. CT will be emphasized as the modality of choice for most oncologic emergencies; however, there are often ancillary roles for ultrasound for initial screening, as well as nuclear medicine studies and MRI for further characterizing previously detected abnormalities. In addition to imaging findings, common clinical presentations will be discussed, as correlation with signs and symptoms adds value to the radiologist’s report and facilitates future imaging.

Vascular

Hemoperitoneum

Spontaneous hemoperitoneum can occur in hypervascular tumors such as hepatocellular carcinoma (HCC), angiosarcoma, pancreatic solid pseudopapillary tumor (SPT), and neuroendocrine tumors. In high HCC-prevalent regions of Asia and Africa, lifetime incidence of spontaneous hemorrhage from HCC can be as high as 14%.5 Rarely, hematogenous malignancies can present with intraperitoneal hemorrhage secondary to coagulopathy. Patients often present with diffuse abdominal pain due to peritoneal inflammation by blood. Larger volume hemorrhages result in hypovolemia, with nausea, hypotension, tachycardia, and eventually shock. Laboratory values may show drop in hematocrit; however, values are often normal. CT is, therefore, critical in diagnosis.

Imaging will demonstrate variable attenuation of blood products depending on acuity. Anemia or dilution by ascites may also decrease attenuation, with typical density of 35 to 45 HU.6 While presence of hemoperitoneum can be detected by noncontrast CT, localizing the source of hemorrhage is facilitated by intravenous contrast administration (Figure 1). Most abdominopelvic CT imaging in the setting of acute abdominal pain will be performed in the portal venous phase, which can identify the presence of hemoperitoneum, as well as demonstrate the sentinel clot sign, which may help localize the likely site of active bleeding. Clotted blood is of higher attenuation (45 to 70 HU), which will stand out against the background of nonclotted blood. Imaging in the arterial phase with CT angiography (CTA) can demonstrate and localize active arterial extravasation and guide further treatment by surgical or interventional radiology teams.

Trauma may complicate interpretation because certain tumors are more vulnerable to injury than adjacent normal parenchyma. For instance, a small liver HCC could potentially hemorrhage after minor blunt trauma and be misinterpreted as a laceration. A spleen that is enlarged due to lymphoma involvement is similarly at increased risk for rupture.7 Careful review of history and ancillary findings aids appropriate diagnosis.

Immediate treatment consists of intravenous infusion of fluids and blood products to improve hemodynamic stability. Correction of coagulopathy is also attempted to the extent possible with platelets and clotting factors. Surgery or targeted embolization should also be considered for focal masses with life-threatening hemorrhage.

Acute Gastrointestinal Hemorrhage

Malignancy is an uncommon cause of gastrointestinal (GI) bleeding, comprising approximately 7% of lower GI bleeds.8 Focal hemorrhage due to cancer in the bowel is almost exclusively due to primary adenocarcinoma, which causes diffuse mucosal ulceration and/or erosion into adjacent vessels. Rare hemorrhages caused by direct vascular invasion by other aggressive abdominal tumors (such as HCC or pancreatic adenocarcinoma) have been reported.9 Hemorrhage over a long segment of bowel may also occur as a consequence of treatment for hematologic disease. Twenty percent of patients with graft vs host disease (GVHD) after allogenic marrow transplant will suffer from diffuse or long segment moderate-severe GI bleeding, usually from the small bowel.10

Gastrointestinal hemorrhage secondary to cancer is frequently low volume and not radiographically evident.11 A hemorrhage rate of at least 0.35 ml/min is typically required for CTA detection, which will demonstrate focal hyperdense contrast extravasation within the bowel lumen.12 A circumferential or focal mass in the bowel may be detected; however, these are often small. When utilizing CTA to evaluate for acute GI bleed, it is imperative that oral contrast not be administered, as it will obscure a typically small volume of intra-arterial contrast extravasating into the lumen. GVHD disease usually results in hyperdense fluid in the bowel due to diffuse oozing of blood. It is accompanied by long-segment small bowel wall thickening and smooth central enhancement (Figure 2).

As an alternative to CTA, Tc-99m red blood cell (RBC) scintigraphy is more sensitive for bleeding, requiring a rate of at least 0.2 ml/min to detect active hemorrhage.12 The longer imaging time of scintigraphy also improves the detection of intermittent bleeds. Imaging of an active bleed will demonstrate accumulation of a radiotracer in the bowel outside of the intravascular compartment (Figure 3). Continued imaging may show a radiotracer in transit along the course of the bowel by peristalsis. Despite the increased sensitivity of scintigraphy, CTA is preferred at most institutions because of more accurate localization and improved detection of soft-tissue findings. Of note, some limitations on nuclear medicine exams may improve with hybrid SPECT/CT imaging.

Catheter-directed angiography requires a rate of at least 1 ml/min for diagnostic localization of an active hemorrhage but has the added advantage of allowing concurrent therapeutic embolization.12 This modality is most useful for cases of massive bleeding (the requirement of transfusion of at least 4 units of blood over 24 hours or hypotension with systolic blood pressure < 90 mm Hg) or when endoscopic management has failed.13 Both scintigraphy and CTA are useful for guiding interventional radiology, endoscopic, and surgical procedures.

Acute Venous Thrombosis and Thromboembolic Events

Approximately 3% of all cases of acute mesenteric thrombosis affect the veins, and malignancy is found in a subset of 4% to 16% of these cases (most commonly myeloproliferative disorders).14,15 Mesenteric thrombosis is much less common than deep venous thrombosis and pulmonary embolism, but shares the common mechanism of over-expression of procoagulant factors by both tumor cells and noncancerous tissue. The classic clinical presentation is pain out of proportion to physical examination findings, which begin with subtle distension and blood in the stool.

Findings are occasionally difficult to identify on CT, with retrospective studies indicating at least 90% accuracy in diagnosis of venous mesenteric thrombosis.14 On portal venous phase contrast-enhanced CT, the filling defect in the mesenteric vasculature appears as a central hypodensity with enhancement of the wall of the affected vessel. Other potential associated findings include portal venous thrombosis and those of intestinal infarction, typified by bowel hypoenhancement, wall thickening, and pneumatosis intestinalis. Although it is rarely considered, catheter-directed mesenteric angiography can be performed in indeterminate cases and would demonstrate a filling defect with late opacification of the proximal vein.16

Treatment with anti-angiogenic agents has also been shown to result in arterial and/or venous thrombotic events (Figure 4).17 This is most common in patients treated with bevacizumab for metastatic colorectal cancer, with relative risks of 1.3 for venous and 1.6 for arterial thromboembolic events.18 The exact mechanism by which thrombosis occurs is not clear, but theories propose that inhibition of VEGF increases vascular inflammation and viscosity/platelet aggregation.

Overall patient survival is better for venous ischemia compared to arterial ischemia but will depend on the specific course of the patient’s cancer.19 Those with limited disease can be treated with systemic anticoagulation and bowel rest, while emergent surgical resection is indicated when bowel infarction has occurred.

Pancreaticobiliary

Obstruction

Pancreatic, ampullary, duodenal, bile duct, and hepatic tumors can result in pancreaticobiliary obstruction, usually by direct invasion or compression of the ducts. Typically, common bile duct (CBD) obstruction is caused by pancreatic ductal adenocarcinoma, followed by invasive cholangiocarcinoma and gallbladder carcinoma. However, any sufficiently large tumor can obstruct ducts by mass effect (Figure 5). Fifty-five percent of patients with pancreatic ductal adenocarcinoma will present with jaundice due to conjugated hyperbilirubinemia, which progressively worsens as the obstruction becomes complete.20 Although the classically suspicious symptom for cancer is painless jaundice, 79% of patients with pancreatic ductal adenocarcinoma present with epigastric pain. Left untreated, obstruction may lead to cholangitis.

The initial imaging test ordered to evaluate obstruction will depend on clinical suspicion. CT is comparable to endoscopic retrograde cholangiopancreatography (ERCP) in establishing the presence of malignant extrahepatic obstruction. In addition to being noninvasive, CT can show ancillary findings such as metastases. Ultrasound is significantly worse for diagnosis (sensitivity of 57%); however, due to its low cost it may be used as the initial study when benign disease is suspected.21 When no obvious mass is identified, MR cholangiopancreatography (MRCP) should be considered.

Strict size criteria for diagnosing CBD dilation are controversial; however, a simple formula of 6 mm plus 1 mm for each decade after age 60 is generally accepted.22 The size of the common bile duct may also be increased after cholecystectomy, with potential normal dilation of up to 10 mm.23 Intrahepatic ductal dilation can be defined as ductal size > 2 mm or > 40% of the adjacent portal vein.24 Dilation of both the intra- and extrahepatic ducts is more suspicious for obstructing malignancy than dilation of the extrahepatic ducts alone. Dilation of intrahepatic ducts alone may suggest a hilar or intrahepatic malignancy.

Endoscopic stenting may be initially used as a bridge to surgery, or for palliation in patients with unresectable disease. Stents do not interfere with the ability to perform subsequent pancreaticoduodenectomy. Strictures that cannot be traversed with an internal drain require percutaneous external biliary drain placement to decompress the biliary ducts.25

Cholecystitis

Gallbladder carcinoma is a rare malignancy that rarely causes acute cholecystitis. Adenocarcinoma represents 90% of cases, with the remainder consisting of squamous, adenosquamous, lymphoma, small cell, and sarcoma malignancies. The rate of incidental gallbladder carcinoma in patients undergoing cholecystectomy for acute cholecystitis in the US is approximately 0.5% but may be as high as 2.3% in East Asia.26 As symptoms are related to cystic duct obstruction by the tumor, they closely mimic symptoms of calculous cholecystitis, with acute right upper quadrant pain, fever, and Murphy’s sign.

Gallbladder carcinoma is usually advanced at presentation and has a propensity for invading the adjacent liver (Figure 6). Many cases present with metastases or bulky porta hepatis and para-aortic lymphadenopathy, with only 25% of these treated with potentially curative resection.27 A minority of patients with gallbladder carcinoma have subtle findings, which can make prospectively differentiating acute cholecystitis from early gallbladder cancer difficult. A small study has demonstrated that elevated C-reactive protein level and less regional fat stranding are reliable indicators of gallbladder cancer, while cholelithiasis and leukocytosis are not.28 Irregular wall thickening was useful when present, but only 20% of cancers were polypoid in morphology with the rest infiltrative. The presence of cholelithiasis is not a useful discriminating factor because most patients with gallbladder cancer have gallstones—in fact, larger stones and longer duration of cholelithiasis are both major risk factors for developing gallbladder carcinoma.29 While white blood cell (WBC) counts tend to be higher in acute cholecystitis by itself, WBC counts are also usually abnormal in gallbladder carcinoma with acute cholecystitis due to acute inflammation.30

Cholecystitis in the setting of gallbladder malignancy may be addressed definitively by surgery in certain circumstances. Simple laparoscopic cholecystectomy is considered appropriate for T1a disease, with cure rates ranging from 85% to 100% if negative margins are attained. Only retrospective studies are available as to outcomes for more advanced disease; however, most show that more radical surgery portends better outcomes.31 An extended cholecystectomy at a minimum involves resection of a rim of hepatic segments IVb and V. T4 disease, which invades the main portal vein, hepatic artery, or multiple extrahepatic organs, is unresectable and best suited to palliative care such as cholecystostomy.

Cholecystitis has also been reported in a small number of cases as a treatment-related side effect from immune checkpoint inhibitor therapy. In contrast to cystic duct obstruction by invasion or compression, the cause is believed to be an autoimmune-related inflammatory state in the gallbladder. These cases were seen in association with drugs targeted to the PD-L1 / PD-1 and CTLA-4 pathways. The role of steroids has not yet been defined, so these cases are managed similarly to cases of typical cholecystitis.32

Bowel

Obstruction

Malignancy is a common cause of obstruction of both the small and large bowel. Approximately 20% of small bowel obstructions are due to tumors, predominantly metastases from ovarian, colonic, pancreatic, and gastric neoplasms.33 Of primary small bowel tumors resulting in obstruction, gastrointestinal stromal tumors (GIST) are most common, followed by lymphoma and adenocarcinoma.34 In the large bowel, roughly 70% of all obstructions are due to neoplasm, with almost one-fifth of all cases of colon cancer complicated by obstruction at some point. Usually this is due to locally advanced but resectable primary adenocarcinoma. A minority of bowel obstructions occur with lymphoma and noncolonic neoplasms such as pancreatic and ovarian cancer.35 Patients with acute obstruction will present with abdominal distension, signs of dehydration, and a tympanic abdomen. Often the slow growth of tumors leads to an insidious onset with postprandial discomfort and nausea leading up to acute complete obstruction. 

Radiography of acute small bowel obstruction demonstrates dilated bowel loops with air-fluid levels; however, contrast-enhanced CT has become the imaging modality of choice.36 CT better shows the location, severity, etiology, and complications of obstruction. Classically, the tumor is located in the ileum and results in enhancing short segment thickening of the bowel wall, with upstream dilation. Masses often serve as a lead point for intussusception, which produces a bowel-within-bowel appearance. The small bowel feces sign (Figure 7) appears as gas and particulate matter just proximal to the mass, pointing to the site of obstruction.37 

In the large bowel, the classic obstructing tumor is in the rectosigmoid colon, the same location for the most common nonmalignant source of large bowel obstruction, sigmoid volvulus. Because of the colon’s greater capacity to distend, adenocarcinoma classically produces a circumferential “apple core” lesion (Figure 8). Upstream dilation varies but can measure > 8 cm proximal to the transition point.38

Emergent surgery should be performed in cases where perforation or ischemia is evident, manifested by pneumatosis intestinalis or portal venous gas.39 In the large bowel, flexible sigmoidoscopy, often with endoscopic stenting (Figure 9) appears reasonably successful for preoperative decompression or palliation.40

Ischemia, Perforation, and Fistula

These rare GI oncologic complications can occur spontaneously but are increasingly likely to be related to targeted drug and radiation treatments. The complications of ischemia, perforation, and fistula share several common suspected mechanisms related to pressure necrosis, mural infiltration by malignant cells, and/or inflammation due to radiation and chemotherapy.41 Patients will usually present with abdominal pain, nausea, and fever. Of note, as many as 12.5% of patients with tumor-bowel fistulas will be asymptomatic at diagnosis. Intravenous and oral contrast-enhanced CT is the imaging study of choice.

The most common causes of tumor-bowel fistulas (TBF) are bulky cervical, ovarian, and colon cancers. Primary small bowel tumors and lymphoma are rarely associated. Tumor size is the primary risk factor, with case studies reporting 8 to 26 cm.42 Another important risk factor is chemoradiotherapy. A case study of 2096 cervical cancers found that all 38 patients who developed TBFs had undergone prior radiation therapy.43 TBF should be suspected on imaging when gas is present within a tumor; however, gas may also be a sign of bacterial infection. In unclear cases, the administration of oral contrast allows for a more confident diagnosis when contrast is seen extending into the tumor. A tract between the tumor and nearby bowel can often be appreciated on reformats (Figure 10).

The risk of tumor-related perforation is highest in ovarian, pancreatic, colon, and rectal cancers. Molecular targeted therapy with antiangiogenic drugs is particularly associated with perforation, and to a lesser extent, fistula. For instance, treatment with bevacizumab (a monoclonal antibody which inhibits VEGF-A) carries a risk of bowel perforation between 1% and 4%.44 On imaging, gas and fluid are usually proximal to the site of perforation (Figure 11). Large bowel perforations can result in massive pneumoperitoneum, whereas small bowel perforations can be more difficult to detect. In some cases, the gas remains closely localized to the site of perforation due to containment by inflammatory reaction.

Early discontinuation of treatment is important for initial treatment of both TBF and perforation, as stopping molecular targeted therapy is associated with reversal of pneumatosis.45 Definitive management requires surgical resection, but conservative management can be attempted in the absence of peritonitis or sepsis.

Genitourinary

Urinary Tract Obstruction

In addition to urothelial cell carcinoma (UCC), urinary tract obstruction occurs often in patients with a variety of malignancies involving the retroperitoneum and pelvis including colon, ovary, and prostate neoplasms causing direct invasion or compression. Malignant urinary obstruction is an ominous development, with a median survival time of 3 months.46 Lymphoma/lymphadenopathy less commonly results in obstruction (Figure 12). Primary urothelial cell carcinoma (UCC) of the ureter is exceedingly rare, occurring approximately 100 times less frequently than UCC of the bladder. In addition to pain, patients are at high risk for developing sepsis related to obstruction and may also develop hypertension from electrolyte and water retention. Symptoms are variable depending on the acuity of obstruction. When due to unilateral external compression, patients are often initially asymptomatic because of the slow progression of disease.

In order of increasing preference, ultrasound, CT without contrast, contrast-enhanced CT, and CT/MR urography can be used to image malignant obstruction. Noncontrast CT and ultrasound are often performed in the emergent setting because of concurrent acute renal failure, prohibiting the use of intravenous contrast. While any portion of the collecting system can be involved, the distal third of the ureter is a frequent site (Figure 13).47 Proximally, the collecting system will be dilated with the kidney demonstrating a delayed nephrogram on contrast-enhanced CT. A delayed nephrogram (Figure 14) appears as reduction of the normal renal parenchymal enhancement in the later phases of contrast excretion (the time point when venous-phase CT is performed). An infiltrating mass with adjacent fat stranding will often be seen in the renal pelvis or ureter in cases of UCC, occasionally appearing as an intrarenal mass when arising in a more proximal calyx. If no definite mass is identified, then irregular narrowing of the ureteral lumen can be a helpful sign.48 Although infrequently performed by radiologists, retrograde pyelography may show contrast within the interstices of a UCC (stipple sign) and distal cupping of intraluminal tumor by contrast (goblet sign).

The three general categories of treatment for acute genitourinary obstruction are: palliation, treatment of extrinsic compression, and surgery. In the case of obstruction by metastasis, the usual approach is by palliation of symptoms with retrograde placement of a ureteric stent. If this cannot be accomplished, percutaneous nephrostomy catheter placement will relieve the obstruction but is more invasive and requires an external drainage bag. For extrinsic compression, treatment of the offending mass should resolve the obstruction; however, stents or nephrostomy tubes may be used as temporizing measures. Lastly, ureteral diversion surgeries can be considerered.47

Acute Adnexal Torsion

Ovarian cysts and masses are the primary risk factors for adnexal torsion. Two case series of patients with ovarian torsion found that 31% to 46% had an ovarian mass, with most of the remainder having simple and hemorrhagic cysts.49,50 Torsion is overwhelmingly more likely to occur in patients with benign masses. A potential explanation is that malignant masses preferentially develop a fixating desmoplastic reaction. Acute adnexal torsion is most likely to occur in patients of reproductive age. Pregnant patients are at particular risk, probably due to hypermobile ligaments.51 Patients present with acute pelvic pain, nausea, and sometimes fever. The pain may be intermittent due to spontaneous detorsion and retorsion.

Initial investigation for torsion should be performed by ultrasound. The most reliable finding on ultrasound is an enlarged ovary, measuring > 20 ml in volume or > 4 cm in greatest dimension. The ovary may also demonstrate stromal edema and heterogeneity due to vascular outflow obstruction. An infrequent but specific sign for adnexal torsion is the twisted vascular pedicle (whirlpool sign). This manifests as a hyperechoic mass adjacent to the ovary with central hypoechoic vessels, sometimes with a beak-like interface. Unlike in the testes, arterial spectral Doppler waveforms may be preserved because of its dual-ovarian blood supply from uterine collaterals and the ovarian artery. Masses serving as lead points will have variable imaging appearance. Mature cystic teratoma is the most common mass seen in torsion, with benign serous cystadenoma slightly less likely (Figure 15).52

While CT should not be performed as the primary modality in cases of suspected ovarian torsion, it may be the first line of imaging when symptoms and history are atypical. In addition to the ovary appearing enlarged and displaced, the uterus is often displaced toward the side of torsion. In less than one-third of cases, a twisting of the vascular pedicle in the affected adnexa can be visualized. Absent enhancement is a worrying sign for infarction of the ovary. MRI is not typically utilized in the emergent setting due to the ease of ultrasound but demonstrates a similar pattern of findings as described with CT, with T1 hypointense/T2 hyperintense edema.

Adnexal torsion, if not treated promptly, can lead to ovarian necrosis and infertility. Patients with an ovarian mass suspicious for malignancy require salpingo-oophorectomy, whereas benign cysts may be treated with cystectomy and detorsion/fixation of the ovary.53

Conclusion

Oncologic emergencies of the abdomen and pelvis are life-threatening events of increasingly common incidence affecting the vascular, pancreaticobiliary, GI, and genitourinary systems. The radiologist should be able to quickly and accurately detect these findings. In patients with known cancer on treatment, clinical information should be integrated into interpretation to identify potential treatment-related emergencies.

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Ruppell E, Kotecha H, McIntosh L.  Oncologic Emergencies of the Abdomen and Pelvis.  J Am Osteopath Coll Radiol.  2020;9(2):11-20.

About the Author

Evan Ruppell, D.O., Hemang Kotecha, D.O., Lacey McIntosh, D.O.

Evan Ruppell, D.O., Hemang Kotecha, D.O., Lacey McIntosh, D.O.

Department of Radiology, UMass Memorial Medical Center, Worcester, MA


 

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