【How to Evaluate Abdominal Distention & Masses: Clinical Clues Hidden Behind a "Bloated Belly"】　ー　Med Student's Study Room

“It’s just some bloating, right?” — Not always. What seems like simple distention can sometimes hide urgent or even life-threatening pathology. This guide walks you through a structured approach to identifying what’s really going on underneath that swollen abdomen.

What You Will Learn

A clear framework for abdominal distention: “acute vs chronic” × “localized vs generalized”
How to interpret CT findings step-by-step in suspected obstruction
Red flag symptoms, common pitfalls, and tips for clinical communication

Let’s begin by meeting a patient whose symptoms might sound familiar…

Opening Case

Patient: 72-year-old woman
Chief Complaint: “My belly’s been bloated for a few days and I haven’t felt like eating.”
Vital Signs: T 36.8℃, HR 88, BP 132/76, RR 16, SpO₂ 97% (room air)
Initial Impression: Mild abdominal tenderness, mildly hyperactive bowel sounds, slight fatigue on face

How should we approach this seemingly simple complaint?

How Should We Approach This?

When we hear “abdominal distention,” many of us think: gas. But the truth is, not all bloating is gas, and not all gas is benign. A visibly distended abdomen can arise from a wide range of causes — and some may require immediate action.

This is where we apply the clinical reasoning framework of Fact → Problem → Hypothesis (FPH). Let’s walk through it:

Fact → Problem → Hypothesis

Fact: Patient reports several days of bloating, loss of appetite, no bowel movements, and mild fatigue.
Problem: Subacute, progressive abdominal distention without flatus or stool — suggests a possible mechanical issue.
Hypothesis: Using the “5Fs” of abdominal distention:
- Fat (obesity)
- Fluid (ascites, urine retention)
- Fetus (pregnancy)
- Flatus (gas from ileus, SBO)
- Feces (impaction)

Among these, the main suspects here are:

Obstruction (SBO, hernia, tumor)
Fluid accumulation (ascites, urinary retention)
Less likely but worth excluding: Masses, Pseudobstruction, or Peritonitis

Now that we’ve outlined our hypotheses, let’s move into Step 1: history taking.

Step 1: History Taking – How to Narrow Down the Cause

Once abdominal distention is recognized, the key is to determine what’s behind it — gas, fluid, mass, or something else. To do this, a thorough history is crucial. We start with the OPQRST format for symptom characterization, followed by the PAM HITS FOSS checklist to explore underlying risk factors and systemic clues.

🩺 OPQRST for Abdominal Distention

Onset: When did the bloating begin? Sudden onset might suggest obstruction or perforation. Gradual progression is more common in ascites or tumors.
Provocation / Palliation: Does it get worse after meals? Relieved by bowel movement or passing gas? Persistent distention unrelieved by passing flatus could point toward a fixed obstruction or mass.
Quality: Is the sensation more of pressure, heaviness, tightness, or pain? A colicky pain pattern suggests obstruction; a dull fullness may reflect ascites or constipation.
Region / Radiation: Where is it most pronounced — upper, lower, or entire abdomen? Does it radiate to the flanks or back?
Severity: How uncomfortable is it on a scale from 1 to 10?
Time course: Has it worsened steadily, fluctuated throughout the day, or remained the same?

Pay attention to symptom evolution — a patient who initially had intermittent bloating that is now constant, with loss of appetite or absence of stool, may be progressing from partial to complete obstruction.

📋 PAM HITS FOSS – Exploring the Bigger Picture

This structured mnemonic helps identify predisposing factors and hidden causes:

Previous episodes / Past medical history: Prior bowel obstructions, IBS, ascites, or liver disease?
Allergies: Medication allergies (e.g., antibiotics → C. difficile colitis)?
Medications & Supplements: Opioids, anticholinergics, iron or calcium supplements? All may reduce GI motility.
Hospitalizations: Especially surgical admissions — risk for adhesions and postoperative ileus.
Injury: Any history of abdominal trauma?
Trauma: Repeat to assess recent injury or abdominal wall hernias.
Surgery: Abdominal or pelvic surgeries? High risk for adhesions or hernias.
Family history: Colorectal cancer, ovarian tumors, liver disease?
OBGYN history: For female patients: pregnancy, ovarian cysts, fibroids, endometriosis.
Sexual history: Risk factors for PID (pelvic inflammatory disease), tubo-ovarian abscess.
Social history:
- Smoking – risk for vascular disease or cancer
- Alcohol – liver disease → ascites, varices
- Drug use – opioids (constipation), stimulants
- Occupation – physical strain → hernia?
- Diet – low fiber? recent change in intake?
- Stress and sleep – link to functional GI disorders like IBS
- Exercise habits – sedentary lifestyle may contribute to constipation

Taken together, this information helps guide us toward differentials such as small bowel obstruction due to adhesions, paralytic ileus from infection or drugs, malignant ascites, functional bloating, or gynecologic masses.

With these hypotheses in mind, let’s move on to the physical examination — where the abdomen may tell us even more.

Step 2: Physical Examination – Listen Carefully, Feel Methodically

Once history raises suspicion for a pathological cause of abdominal distention, physical examination helps confirm or refute your hypotheses. A structured approach improves accuracy and avoids missing subtle red flags.

🔍 General Impression

Does the patient appear toxic, diaphoretic, or fatigued?
Is the patient writhing in pain (suggestive of obstruction) or lying still (peritonitis)?

👀 Inspection

Visible distention — localized (e.g. hernia, mass) or diffuse (e.g. ascites, obstruction)?
Surgical scars → risk of adhesions
Visible peristalsis → may suggest distal obstruction
Skin changes → caput medusae, striae (ascites), ecchymosis (e.g. Cullen’s sign)

🎧 Auscultation

Hyperactive bowel sounds: “tinkling” high-pitched → early obstruction
Hypoactive/absent sounds: late obstruction, ileus, or peritonitis
Splashing sound: Listen for a “sloshing” sound (succussion splash) when rocking the patient gently → retained fluid in stomach or intestines

⚒ Percussion

Tympanic: Gas distention (flatus, bowel obstruction)
Dullness: Suggests fluid (ascites), mass, or solid organ enlargement
Shifting dullness: Classic sign of free fluid — percuss with patient supine and again in lateral decubitus

✋ Palpation

Localized tenderness: Suggests inflammatory cause (e.g. appendicitis, diverticulitis)
Rebound tenderness / Guarding: Peritonitis or ischemia
Palpable mass: May be a hernia, tumor, or distended organ
Fluid wave: Suggests ascites — tap one flank while feeling the impulse on the opposite side
Fluctuation test: For confirming fluid-filled cavity (e.g. cysts, large ascites)

🩺 Special Exams

Rectal exam: Check for stool burden, masses, bleeding
Pelvic exam: In female patients with lower abdominal pain or bloating, consider ovarian pathology
Hernia exam: Don’t forget to examine inguinal, femoral, and umbilical areas for reducible or strangulated hernias

🧠 Clinical Synthesis

Hyperactive bowel sounds + tympany + peristalsis = likely mechanical obstruction
Diffuse dullness + shifting dullness = ascites
No bowel sounds + tenderness + guarding = surgical abdomen (e.g. peritonitis, strangulation)

💡 Clinical Tip: How to Detect a Splashing Sound

The “succussion splash” is a sloshing noise heard during sudden movement — often described as a “water-in-a-bottle” sound. It suggests fluid retention in the stomach or intestines, commonly in gastric outlet obstruction or advanced ileus.

Now that we’ve gathered strong clues from the physical exam, let’s shift toward the next step: diagnostic testing — starting with labs and imaging.

Step 3: Diagnostic Workup – Imaging and Labs That Matter

Based on the clinical history and physical findings, it’s time to solidify our working diagnosis with focused investigations. The goal is to confirm or exclude mechanical obstruction, identify fluid shifts, and rule out surgical emergencies.

📊 Basic Laboratory Tests

WBC / CRP: Inflammation or infection — elevated in peritonitis, ischemia, strangulation
Electrolytes: Hypokalemia or metabolic alkalosis in vomiting; hyponatremia in fluid overload or SIADH
Liver function tests: Assess for cirrhosis, biliary obstruction
Renal function (BUN/Creatinine): Evaluate volume status, urinary retention, or obstruction
Urinalysis: Rule out UTI, hematuria, or obstructive uropathy
Pregnancy test (β-hCG): Mandatory in reproductive-aged females
Tumor markers: CA-125, CEA, CA 19-9 — helpful if malignancy or ovarian mass is suspected

🖼 Abdominal Imaging – First Steps

📷 Abdominal X-ray (AXR)

Useful for: Initial screening in suspected obstruction or constipation
Findings to look for:
- Dilated loops of bowel
- Air-fluid levels (ladder-like)
- Absence of rectal gas → suggestive of complete obstruction
- Free air under diaphragm → perforation

🧠 Tip: Don’t be deceived by “air everywhere” — it could still be early SBO before full dilation sets in.

🖥 CT Scan – Stepwise Approach to Obstruction

CT is the gold standard for evaluating small bowel obstruction. Follow a structured reading strategy:

🟦 Stepwise Approach to CT

Look for dilated loops: Small bowel > 3 cm is suggestive
Check the ileocecal junction: Is the terminal ileum collapsed (transition point)?
Assess the mesentery: SMA > SMV caliber suggests strangulation risk
Evaluate oral to anal continuity: Identify transition zone and downstream decompression
Identify obstruction signs:
- Small bowel feces sign – feces-like content in dilated bowel
- Beak sign – tapered point at obstruction site
- Whirl sign – twisted mesentery, seen in volvulus or strangulation

🔴 Red Flags for Strangulation or Ischemia

Thickened bowel wall (edema, >3 mm)
Misty mesentery: Fat stranding or congestion
High-density ascites: CT attenuation > 20 HU → suggests hemoperitoneum or infection
Reduced bowel wall enhancement → suspect ischemia
Abdominal wall thickening / fascial edema

💡 Column: Internal vs External Hernia – How to Tell

External hernias (inguinal, femoral, umbilical) are usually palpable on exam. They often show a transition point near the abdominal wall.

Internal hernias are trickier — no external bulge. Look for clustered loops, swirl signs, or unexpected transition zones in the mesentery.

💧 Ascites Evaluation

On imaging, ascites may layer out and cause diffuse abdominal distention
High-density ascites (CT attenuation > 20) → suspect malignant, hemorrhagic, or infectious cause
Consider paracentesis for analysis if diagnosis remains unclear:
- SAAG (serum-ascites albumin gradient)
- Cell count, culture, cytology

🧸 Column: Third Space Fluid Shift – A Hidden Cause of Hypovolemia

Not all fluid loss is visible. In conditions like ileus, pancreatitis, or peritonitis, large amounts of fluid can move out of the vasculature into the peritoneal cavity or bowel wall — this is known as a third space shift.

Mechanism: Inflammation increases capillary permeability → plasma-like fluid leaks into the bowel lumen or peritoneum.
Consequences: Despite a distended abdomen, the patient may be intravascularly hypovolemic — leading to tachycardia, hypotension, or prerenal azotemia.
Examples: Acute pancreatitis, SBO with vomiting, peritonitis, or trauma.

Always evaluate volume status clinically and consider early IV fluid resuscitation if signs of hypoperfusion are present.

For more details on this topic, see our related article:
🩺 Hypovolemia: Clinical Clues to Catch Before the Collapse

Now that our diagnostics are complete, let’s circle back to our original case and walk through how these findings apply in real time.

➡️ Case Reflection: Reapplying Step 1–3 to Our Patient

Now that we’ve gone through the structured diagnostic steps, let’s return to our original case of the 72-year-old woman who presented with several days of abdominal distention and poor appetite.

🔎 Step 1: Reassessing History

Physician: “How long have you been feeling bloated?”
Patient: “It started about three days ago. I haven’t really wanted to eat anything.”
Physician: “Any vomiting or bowel movements since then?”
Patient: “No vomiting, but I haven’t had a bowel movement either.”
Physician: “Any prior surgeries or similar symptoms in the past?”
Patient: “I had surgery for a hernia about 10 years ago. Nothing like this before though.”

Fact: Persistent bloating, anorexia, and constipation without vomiting.
Problem: Subacute abdominal distention with absent stool, prior hernia repair.
Hypotheses: True obstruction (adhesions, hernia recurrence), functional ileus, large mass, urinary retention, ascites.

👀 Step 2: Reassessing Physical Examination

Inspection: Visible abdominal distention
Auscultation: Hyperactive bowel sounds (“tinkling”)
Percussion: Tympanic sounds in mid-abdomen, shifting dullness noted laterally
Palpation: Mild tenderness, no rebound or guarding
Rectal exam: Empty rectum, no mass

These findings raise concern for small bowel obstruction with possible fluid accumulation (ascites or third spacing).

📍 Step 3: Reassessing Investigations

Labs: Mild leukocytosis, elevated CRP, normal renal/liver function, negative pregnancy test
AXR: Dilated loops with air-fluid levels, no rectal gas
CT: Small bowel loops >3.5 cm, beak sign near old hernia site, misty mesentery, high-density ascites (25 HU), thickened bowel wall

Interpretation: Suggestive of strangulated small bowel obstruction (likely due to incarcerated hernia).

🏥 Turning Point

The patient was diagnosed with a strangulated small bowel obstruction due to an incarcerated external hernia. Emergency surgical consultation was initiated. Intraoperative findings confirmed the presence of ischemic bowel loops requiring partial resection.

This case reminds us that even “just bloated” can mask life-threatening conditions. A stepwise evaluation is not only diagnostic, but often life-saving.

Now that we’ve walked through the case using all three steps, it’s time to think practically: When should we call in a specialist? In the next section, we’ll break down the red flags and decision points for timely referral to surgery or other disciplines.

🚪 When to Refer to a Specialist – Surgical or Otherwise?

Not every case of abdominal distention requires a specialist, but recognizing the right timing can be life-saving. Let’s walk through some clear indicators that signal the need for consultation, especially to surgery or gastroenterology.

🚑 Urgent Surgical Referral

Strangulated hernia or suspected ischemic bowel: CT findings like whirl sign, thickened bowel wall, and high-density ascites
Peritonitis: Guarding, rebound tenderness, or signs of sepsis
Free air under diaphragm: Suggestive of perforation → emergent intervention
Failure of conservative management: If symptoms persist despite bowel rest and decompression

🏛 GI or Internal Medicine Consultation

New-onset ascites: Requires diagnostic paracentesis and etiology workup
Chronic or recurrent bloating: To evaluate for IBS, motility disorders, or SIBO
Suspicion for malignancy: If imaging reveals mass or elevated tumor markers
Persistent constipation: To assess for colonic inertia, obstruction, or functional syndromes

In many cases, early involvement of specialists leads to better outcomes and more efficient workup. Don’t hesitate to escalate when red flags appear.

Next, let’s dive into some practical bedside tips — how to distinguish true obstruction from pseudo-distention, and how to maximize your physical exam.

🔧 Clinical Tips – Exam & Interpretation at the Bedside

✅ History Taking

Always clarify if the sensation is subjective bloating or visible abdominal distention
Ask about bowel movements and flatus — a key to detecting obstruction
Don’t forget to ask about prior surgeries (especially hernia repairs, abdominal/pelvic surgery)
Women of reproductive age: always ask about menstrual cycle and pregnancy risk

✅ Physical Exam

Shifting dullness: A sign of ascites when percussion dullness moves with patient position
Succussion splash: “Sloshing” sound on rocking the patient → suggests retained gastric fluid in SBO or gastric outlet obstruction
Tympanic percussion: Indicates gas-filled distention — helps distinguish between gas and fluid/mass
Visible peristalsis: May be seen in thin patients with obstruction → look near the umbilicus

✅ Imaging & Decision-Making

CT first? If you suspect obstruction, a contrast-enhanced CT is the best initial imaging
Don’t delay imaging: Red flag symptoms warrant urgent scanning, even in stable vitals
Recheck imaging dynamically: Compare old CTs or watch for progression on serial films
High-density ascites: Think hemorrhage, malignancy, or infection (CT attenuation > 20 HU)

Up next: wisdom from seasoned clinicians. Let’s take a look at some memorable Clinical Pearls to keep in mind.

🔹 Clinical Pearls

“Don’t be fooled by the gas: not all distention is benign.” — Anonymous surgical resident
“The abdomen doesn’t lie — listen, percuss, and trust your exam.” — Dr. R. M., Gastroenterologist
“Succussion splash is the forgotten clue in gastric outlet obstruction.” — From a 1980s physical diagnosis textbook
“Air-fluid levels are the language of the bowel. Learn to read them.” — Radiology attending at morning rounds

Next, let’s go hands-on with English. Time to build your vocabulary and patient-friendly phrasing in our expressions section.

📄 OET Focus: Writing & Speaking Practice (Abdominal Distention)

🖋 Writing Task Example (Discharge Letter)

Prompt: You are a junior doctor in the surgical ward. The following patient has been managed and is now ready for discharge. Write a letter to the patient’s general practitioner, summarizing the clinical course and recommendations.

Patient Details:
Name: Mrs. Ayaka Tanaka
Age: 72
Diagnosis: Strangulated small bowel obstruction due to incarcerated external hernia
Treatment: Emergency laparotomy and partial small bowel resection
Course: Uneventful recovery. Mobilizing and tolerating oral intake.

📃 Sample Referral Letter

Dear Dr. Yamada,

I am writing to inform you about your patient, Mrs. Ayaka Tanaka, a 72-year-old woman who was admitted to our surgical unit with complaints of abdominal distention and anorexia. Upon further assessment and imaging, she was diagnosed with a strangulated small bowel obstruction secondary to an incarcerated external hernia.

An emergency laparotomy was performed on the day of admission. Intraoperative findings revealed ischemic small bowel loops, which necessitated partial resection followed by anastomosis. The procedure was uneventful, and she has made a good recovery.

During her hospital stay, she was managed with intravenous fluids, prophylactic antibiotics, and bowel rest. Postoperatively, she gradually resumed oral intake and is currently mobilizing independently. Her pain is well-controlled with oral analgesics, and her bowel function has returned.

We have advised her to avoid heavy lifting and to monitor for any signs of wound infection or recurrence. A follow-up appointment has been scheduled in our outpatient clinic in two weeks.

Thank you for your continued care of this patient. Please do not hesitate to contact us should you need any further information.

Kind regards,
[Your Name], Resident Surgeon
General Surgery Department

🔊 Speaking Task Ideas

Explaining diagnosis: “We found that a portion of your intestine had become trapped in a weak area of the abdominal wall, which blocked its blood supply. This is called a strangulated hernia.”
Pre-op preparation: “You will need surgery to release the trapped bowel and check for any damage. We’ll ensure your safety with blood tests, IV fluids, and anesthesia assessment.”
Post-op explanation: “You may feel sore, but most patients recover in a few days. It’s important to start walking as soon as possible to prevent complications.”
Lay explanation of CT findings: “The scan showed swollen bowel loops and signs that part of your intestine wasn’t getting enough blood. That’s why we needed to operate quickly.”

🛍️ Summary & Further Reading

In this article, we explored how to evaluate a patient presenting with abdominal distention, from history taking and physical examination to imaging, lab work, and timely specialist referral. We also practiced real-world communication through OET writing and speaking tasks. The key takeaway? Don’t underestimate a “bloated belly”—life-threatening conditions may be hiding beneath the surface.

🔗 Related Articles:

🔹 References

Yamada T, Alpers DH, et al. Textbook of Gastroenterology. 6th ed. Wiley-Blackwell; 2015.
Cope Z. Cope’s Early Diagnosis of the Acute Abdomen. 22nd ed. Oxford University Press; 2010.
Williams NS, O’Connell PR, McCaskie AW. Bailey & Love’s Short Practice of Surgery. 28th ed. CRC Press; 2022.
Japanese Society of Abdominal Emergency Medicine. Guidelines for the Management of Small Bowel Obstruction. 2021.
Royal College of Surgeons. Emergency Surgery: Abdominal Conditions. 2020.