# Clinical Cases: Abdominal Imaging

## Case 1: Small Bowel Obstruction

### Patient Demographics
- **Age:** 68 years old
- **Sex:** Female
- **Occupation:** Retired nurse

### Chief Complaint
Progressive abdominal pain, distension, and vomiting for 48 hours.

### History of Present Illness
The patient presents with crampy, periumbilical abdominal pain that started gradually two days ago. She reports progressive abdominal distension and has vomited multiple times with bilious content. She has not passed flatus or had a bowel movement for 36 hours. Past surgical history is significant for an open appendectomy 25 years ago and a cesarean section 40 years ago. She denies fever, bloody vomiting, or bloody stools.

### Physical Examination
- **Vitals:** HR 98 bpm, BP 128/76 mmHg, RR 18, Temp 37.2C, SpO2 98% on room air
- **General:** Moderate distress, uncomfortable
- **Abdomen:** Distended, tympanic to percussion, high-pitched bowel sounds with occasional rushes, mild diffuse tenderness without peritoneal signs
- **Rectal examination:** Empty rectal vault, no masses, guaiac negative

### Imaging Workup
1. **Supine abdominal radiograph:** Multiple dilated loops of small bowel centrally located with valvulae conniventes visible traversing the entire bowel width. No gas visible in the colon or rectum.
2. **Upright abdominal radiograph:** Multiple air-fluid levels at different heights within the same loop of bowel (differential air-fluid levels), consistent with mechanical small bowel obstruction.
3. **CT abdomen/pelvis with IV contrast:** Dilated small bowel loops up to 4.5 cm proximal to a discrete transition point in the right lower quadrant. The transition zone shows a band-like structure consistent with adhesion. The decompressed distal small bowel confirms mechanical obstruction. No evidence of bowel wall thickening, pneumatosis, or portal venous gas to suggest ischemia.

### Clinical Image
![Small Bowel Obstruction X-ray](case_01_image.jpg)

*Upright abdominal radiograph demonstrating dilated small bowel loops with multiple air-fluid levels characteristic of mechanical small bowel obstruction.*

**Image Source:** Wikimedia Commons - File:Upright X-ray demonstrating small bowel obstruction.jpg by James Heilman, MD, licensed under CC BY-SA 3.0

### Diagnosis
**Adhesive small bowel obstruction** secondary to postoperative adhesions.

### Anatomical Correlation
The imaging findings demonstrate key anatomical features distinguishing small bowel from large bowel. The valvulae conniventes (plicae circulares) are mucosal folds that traverse the entire width of the small bowel lumen and are characteristic of jejunum in particular. In contrast, the haustra of the large bowel are incomplete folds that do not cross the entire lumen. Small bowel is considered dilated when measuring greater than 3 cm on plain radiograph or 2.5 cm on CT. The central location of dilated loops suggests small bowel, as the colon frames the periphery of the abdomen. The "small bowel feces sign" may be seen on CT at the transition point, representing particulate matter mixed with fluid in obstructed small bowel. Adhesions are the most common cause of small bowel obstruction in developed countries, accounting for 65-75% of cases.

### Treatment
1. **Conservative management:** NPO, nasogastric tube decompression, IV fluid resuscitation, electrolyte correction
2. **Serial examinations:** Monitoring for signs of strangulation (fever, tachycardia, localized tenderness, leukocytosis)
3. **Water-soluble contrast challenge:** Gastrografin administration to predict resolution and potentially therapeutic
4. **Surgical intervention:** Laparoscopic adhesiolysis if no resolution within 48-72 hours or if signs of strangulation develop

---

## Case 2: Acute Cholecystitis

### Patient Demographics
- **Age:** 45 years old
- **Sex:** Female
- **Occupation:** Administrative assistant

### Chief Complaint
Severe right upper quadrant pain for 8 hours.

### History of Present Illness
The patient describes the acute onset of constant, severe pain in the right upper quadrant after eating a fatty meal last evening. The pain radiates to her right shoulder and is associated with nausea and two episodes of non-bilious vomiting. She reports having had similar but milder episodes of right upper quadrant discomfort after fatty meals for the past year that would resolve within an hour. This episode is different in that the pain has been constant and more severe. She denies jaundice, dark urine, or light-colored stools.

### Physical Examination
- **Vitals:** HR 92 bpm, BP 138/84 mmHg, RR 16, Temp 38.1C, SpO2 99% on room air
- **General:** Appears uncomfortable, lying still
- **Abdomen:** Soft, positive Murphy sign (arrest of inspiration during palpation of the right upper quadrant), no rebound tenderness, bowel sounds present
- **Skin:** No jaundice or icterus

### Imaging Workup
1. **Right upper quadrant ultrasound (first-line for suspected biliary disease):**
   - Multiple echogenic foci in the gallbladder with posterior acoustic shadowing (gallstones)
   - Gallbladder wall thickening to 5 mm (normal <3 mm)
   - Pericholecystic fluid present
   - Positive sonographic Murphy sign
   - Common bile duct measures 4 mm (normal <6 mm)
2. **Laboratory studies:** WBC 14,500/microL with left shift, AST 42 U/L, ALT 48 U/L, alkaline phosphatase 110 U/L, total bilirubin 1.1 mg/dL

### Diagnosis
**Acute calculous cholecystitis** with characteristic ultrasound findings.

### Anatomical Correlation
Ultrasound is the first-line imaging modality for suspected biliary disease because it has excellent sensitivity for detecting gallstones and does not involve ionizing radiation. Gallstones appear as echogenic (bright) foci with posterior acoustic shadowing because they absorb and reflect the ultrasound beam, preventing transmission to deeper tissues. The normal gallbladder wall measures less than 3 mm in thickness; wall thickening indicates inflammation. Pericholecystic fluid represents inflammatory exudate surrounding the gallbladder. The sonographic Murphy sign is pain elicited when the ultrasound transducer presses the gallbladder against the liver during inspiration. The referred pain to the right shoulder follows the T7-T9 dermatomes, corresponding to the sensory innervation of the gallbladder via the greater splanchnic nerve.

### Treatment
1. **NPO status and IV fluids**
2. **Analgesia and antiemetic medications**
3. **IV antibiotics:** Coverage for enteric gram-negative organisms and anaerobes
4. **Laparoscopic cholecystectomy:** Definitive treatment, preferably within 72 hours of symptom onset

---

## Case 3: Pneumoperitoneum from Perforated Peptic Ulcer

### Patient Demographics
- **Age:** 52 years old
- **Sex:** Male
- **Occupation:** Restaurant manager

### Chief Complaint
Sudden onset of severe epigastric pain.

### History of Present Illness
The patient reports the abrupt onset of severe, constant epigastric pain approximately 6 hours ago. He describes the pain as "like being stabbed" and rates it 10/10 in intensity. The pain has since spread to involve the entire abdomen. He is lying very still because any movement worsens the pain. He has a history of intermittent epigastric discomfort and burning for years, partially relieved by antacids, but never formally evaluated. He smokes one pack of cigarettes daily and takes ibuprofen regularly for chronic back pain. He denies recent vomiting or hematemesis.

### Physical Examination
- **Vitals:** HR 118 bpm, BP 102/68 mmHg, RR 24, Temp 37.8C, SpO2 96% on room air
- **General:** Appears acutely ill, diaphoretic, lying motionless
- **Abdomen:** Board-like rigidity, diffuse tenderness with rebound, absent bowel sounds
- **Rectal examination:** No blood, no masses

### Imaging Workup
1. **Upright chest radiograph:** Free air (pneumoperitoneum) visible as a crescent of lucency beneath the right hemidiaphragm. This is the most sensitive plain radiograph for detecting free intraperitoneal air.
2. **Left lateral decubitus abdominal radiograph:** Confirms free air overlying the lateral liver margin (used when patient cannot sit upright).
3. **CT abdomen/pelvis without and with contrast:** Extensive pneumoperitoneum with free air surrounding the liver and spleen. Focal discontinuity of the anterior wall of the duodenal bulb consistent with perforation. Free fluid in the pelvis.

### Clinical Image
![Pneumoperitoneum X-ray](case_01_image.jpg)

*Upright chest radiograph demonstrating free air beneath the right hemidiaphragm (arrow), indicating pneumoperitoneum from bowel perforation.*

**Image Source:** Wikimedia Commons - Category:X-rays of pneumoperitoneum, Creative Commons Attribution-Share Alike 3.0

### Diagnosis
**Perforated duodenal ulcer** with generalized peritonitis.

### Anatomical Correlation
Free intraperitoneal air rises to the highest point in the peritoneal cavity. In an upright patient, this is beneath the diaphragm, making the upright chest radiograph the most sensitive plain film for detecting pneumoperitoneum. The right hemidiaphragm provides better contrast than the left because the liver creates a homogeneous density below it, whereas the gastric air bubble may mimic free air on the left. In patients who cannot sit upright, a left lateral decubitus film positions free air between the liver and the right lateral abdominal wall. CT is more sensitive than plain radiographs and can detect as little as 5 mL of free air, as well as localize the site of perforation. Duodenal ulcers typically occur in the duodenal bulb (first part of duodenum) and may perforate anteriorly into the peritoneal cavity or posteriorly into the lesser sac, potentially eroding into the gastroduodenal artery.

### Treatment
1. **Immediate resuscitation:** IV fluid bolus, vasopressors if needed
2. **NPO and nasogastric decompression**
3. **Broad-spectrum IV antibiotics**
4. **Emergent surgical repair:** Primary closure with omental patch (Graham patch) or definitive ulcer surgery
5. **Post-operative H. pylori testing and eradication therapy**