What is the differential diagnosis and appropriate workup for a 36-year-old female with a history of ovarian cancer and prior abdominal surgery, presenting with a one-week history of constipation, inability to pass gas, abdominal pain, and bloating, after recent hospitalization for fluid accumulation around her heart, lungs, and abdomen?

Differential Diagnosis and Workup for Bowel Obstruction in Ovarian Cancer Patient

Primary Clinical Assessment

This patient most likely has malignant bowel obstruction (MBO) from progressive ovarian cancer, which is a pre-terminal event requiring urgent evaluation to determine if surgical intervention is appropriate or if medical palliation is the better approach. 1, 2

The clinical picture—inability to pass stool or gas for one week, vomiting, abdominal distension with firmness and tenderness, poor oral intake, and recent recurrent malignant effusions—strongly suggests complete or near-complete bowel obstruction in the setting of advanced ovarian cancer. 1, 3

Differential Diagnosis (in order of likelihood)

Most Likely:

• Malignant bowel obstruction from peritoneal carcinomatosis: This occurs in approximately 17.6% of ovarian cancer patients after initial diagnosis and is typically a pre-terminal event with median survival of 93 days when due to malignancy (versus 382 days when due to adhesions). 3
• Adhesive bowel obstruction: Given her history of prior abdominal surgery, adhesions remain a possibility, though less likely given the context of progressive malignant disease with recurrent effusions. 3

Other Important Considerations:

• Massive ascites causing functional obstruction: Her scheduled paracentesis suggests recurrent ascites, which can compress bowel and mimic obstruction. 4
• Tumor mass directly compressing bowel: Progressive ovarian cancer can cause mechanical obstruction from external compression. 2
• Ileus from metabolic derangements: Hyponatremia, hypercalcemia, or other electrolyte abnormalities from advanced malignancy can cause pseudo-obstruction. 4
• Constipation from poor oral intake and dehydration: Though less likely given inability to pass gas, this should be considered. 5

Immediate Workup (Within 1-4 Hours)

Laboratory Studies (Immediate - Within 1 Hour):

• Complete blood count: To assess for leukocytosis (infection/perforation), anemia (bleeding), or thrombocytosis (hypercoagulable state). 4
• Comprehensive metabolic panel: Critical to evaluate for hyponatremia (SIADH), hypercalcemia (malignancy-related), renal function (dehydration), and liver function. 4
• Fingerstick glucose: Immediate assessment for hypoglycemia or hyperglycemia. 4
• Arterial blood gas: If oxygen saturation <92%, to assess for metabolic acidosis (ischemic bowel) or respiratory compromise. 4
• Lactate level: Elevated lactate suggests bowel ischemia or perforation requiring emergency surgery. 4
• Blood cultures: If fever, leukocytosis, or hemodynamic instability present to rule out sepsis from infected ascites or perforated viscus. 4

Imaging Studies (Urgent - Within 4-6 Hours):

• CT abdomen/pelvis with IV contrast (oral contrast contraindicated in obstruction): This is the gold standard to determine the level and cause of obstruction, assess for perforation, identify transition points, evaluate for ascites volume, and distinguish malignant obstruction from adhesive obstruction. 6, 5
• Upright chest X-ray and abdominal X-ray series: To assess for free air (perforation), air-fluid levels (obstruction), and degree of bowel distension. 4
• Chest X-ray or CT chest: To evaluate for recurrent pleural effusion, which occurs in 50-70% of advanced ovarian cancer and can cause severe hypoxia. 4

Physical Examination Priorities:

• Vital signs including oxygen saturation: Hypotension with abdominal distension requires immediate exclusion of sepsis, massive ascites, or bowel perforation. 4
• Abdominal examination specifics: Assess for peritoneal signs (rigidity, rebound, guarding suggesting perforation), bowel sounds (absent in ileus, high-pitched/tinkling in mechanical obstruction), palpable masses, and degree of distension. 7, 5
• Rectal examination: To assess for impaction, rectal mass, or blood (suggesting ischemia). 6

Critical Decision Points

Surgical Candidacy Assessment:

Surgery should be considered only in patients with good performance status (ECOG 0-2), discrete/single-level obstruction on imaging, ongoing response to chemotherapy, and absence of cachexia. 1, 2

Surgical management is associated with:

• Shorter hospitalization (p=0.02) 1
• More effective pain reduction (p=0.001) 1
• Lower rates of re-obstruction (p=0.02) 1
• Longer median survival after palliation (p=0.025) 1

However, cachexia, poor performance status, and poor nutritional status are significant predictors of worse survival after MBO regardless of treatment approach. 1

Medical Management Indications:

Medical palliation with antisecretory drugs is the standard of care for frail patients, those with multiple levels of obstruction, diffuse carcinomatosis, or poor performance status. 1, 2

Immediate Interventions

Supportive Care (Initiate Immediately):

• NPO status: Nothing by mouth until obstruction is characterized. 2
• Nasogastric tube decompression: For symptomatic relief if vomiting is persistent, though not all patients require this. 2
• IV fluid resuscitation: Aggressive hydration for dehydration from poor oral intake and vomiting. 4
• Pain management: Her 7/10 pain requires immediate analgesia; opioids are appropriate. 1
• Antiemetics: To control nausea and vomiting. 2

Consultation:

• Gynecologic oncology: Urgent consultation to determine surgical candidacy and overall prognosis. 6, 1
• Palliative care: Should be involved early given the pre-terminal nature of MBO in ovarian cancer. 6, 1
• General surgery: If surgical intervention is being considered. 1

Critical Pitfalls to Avoid

• Do not delay imaging: CT scan is essential to distinguish surgical from non-surgical obstruction and to identify perforation. 6, 5
• Do not assume all obstruction requires surgery: In ovarian cancer patients with MBO, median survival is only 93 days when due to malignancy, and many patients are better served with medical palliation. 3
• Do not miss bowel ischemia or perforation: Elevated lactate, peritoneal signs, or free air mandate emergency surgical consultation. 4
• Do not ignore metabolic complications: Hypercalcemia and hyponatremia are common in advanced ovarian cancer and can worsen clinical status. 4
• Do not proceed with scheduled paracentesis tomorrow without first addressing the obstruction: The obstruction takes priority and may change management plans. 4
• Do not attribute symptoms to functional disorders: In a patient with known advanced ovarian cancer and recurrent malignant effusions, MBO is the most likely diagnosis. 7, 5

Prognosis Context

Nearly 20% of advanced ovarian cancer patients develop bowel obstruction, and when due to malignancy rather than adhesions, it signals a pre-terminal event with few patients living more than one year from the time of obstruction. 2, 3 This context is essential for shared decision-making about aggressive versus palliative interventions.