Clinical Analysis: 18-Year-Old Male with Right Iliac Fossa (RIF) Pain

Clinical Summary

Most Likely Diagnosis: Faecel Retention / Loaded Colon with Overflow Effects

1. Voluntarily held urine - leads to a distended bladder
2. A distended bladder + pre-existing constipation (impacted faeces in the caecum/ascending colon and rectum) causes referred and direct pressure pain in the RIF
3. The right colon (caecum + ascending colon) lies directly in the RIF - faecal loading here produces a characteristic tender, doughy mass

Differential Diagnoses (in order of likelihood)

1. Faecal Impaction / Loaded Colon (MOST LIKELY)

• Chronic constipation + anal fissure (he avoids defecation due to pain from the fissure) leads to progressive faecal loading
• Caecal distension causes RIF pain
• The episode of voluntary urinary retention may have worsened visceral discomfort and brought him to attention
• Key features pointing here: chronic constipation, anal fissure (avoidance of defecation), 3-day gradual pain

2. Post-Appendicectomy Adhesion Pain

• Adhesions are a well-known long-term sequela of appendicectomy, even without frank obstruction
• Adhesion bands can kink the terminal ileum or cause intermittent partial small bowel obstruction
• However, 3-day constant pain without vomiting or distension makes complete obstruction less likely
• Key features pointing here: previous appendicectomy 4 years ago, chronic RIF pain

3. Stump Appendicitis (Retained Appendix Stump)

• If the original appendicectomy left a long stump (>0.5 cm), inflammation can recur
• Presents identically to acute appendicitis
• Rare but important to consider in a post-appendicectomy patient with RIF pain
• Key features pointing here: prior appendicectomy, RIF pain, young male

4. Mesenteric Lymphadenitis

• Common in young males, often follows viral URTI
• Tender enlarged mesenteric nodes in RIF
• Key features pointing here: age, sex

5. Testicular Torsion (Do NOT miss)

• A classic "trap" - teen-aged boys with RIF pain are sometimes misdiagnosed as appendicitis when the actual cause is testicular torsion
• As the S Das surgical manual explicitly notes: "Cases are on record when teen-aged boy with the complain of pain in the right iliac fossa was referred to the hospital by the general physician as a case of acute appendicitis. Only after examination of the scrotum, the surgeon found torsion of the testis as the cause of pain"
• MUST examine the scrotum in every male with RIF pain
• Torsion is a surgical emergency - missing it is catastrophic

6. Terminal Ileitis / Crohn's Disease

• Crohn's classically affects the terminal ileum (RIF)
• Constipation + RIF pain + young patient raises this possibility
• Usually associated with diarrhoea but can present atypically

7. Ileocaecal Tuberculosis

• Relevant in endemic regions
• Presents with RIF mass, pain, weight loss
• Should be considered if constitutional symptoms present

8. Psoas Abscess / Iliac Lymphadenitis

• Less likely acutely but can cause RIF pain with hip flexion pain

9. Ureteric Stone (Right-sided)

• The voluntary urinary retention episode raises the possibility of urinary tract involvement
• A stone in the right ureter can cause colicky RIF pain with radiation to the groin
• Urinalysis would show haematuria

The Urinary Retention Angle

• Acute urinary retention - even if self-limited - can cause suprapubic and referred lower abdominal/RIF pain
• A distended bladder presses on adjacent structures (sigmoid, caecum, right iliac vessels)
• In a constipated patient, this "double loading" (faeces + urine) exacerbates pelvic/RIF discomfort considerably
• Urinary retention has been documented as an unusual presenting feature in appendicitis (inflamed appendix irritating the bladder/ureter), but here the sequence is reversed - the retention came first

Investigations Recommended

Key Clinical Priorities

1. Examine the scrotum first - torsion is a time-critical emergency
2. Perform a rectal examination - will confirm faecal loading and assess the anal fissure
3. Urine dipstick - quick, cheap, rules out urinary tract cause
4. Ultrasound - first-line imaging given his age (avoids radiation)
5. Do not anchor on the previous appendicectomy - the appendix stump can still inflame, and many other diagnoses exist

Summary

Bailey and Love's Surgery notes that recurrent RIF pain should prompt consideration of Crohn's disease, and that thorough initial assessment with imaging is essential to reduce misdiagnosis. S Das Manual on Clinical Surgery - p. 12: examination of the scrotum in teen-aged boys with RIF pain is mandatory to exclude torsion.

Updated Diagnosis: Inflamed Bowel Loops on USS - What This Means

Revised Differential Diagnosis (Most to Least Likely)

1. Crohn's Disease (Terminal Ileitis) - TOP DIAGNOSIS

• 18-year-old male (peak onset: 15-35 years)
• Inflamed bowel loops in RIF (terminal ileum is the most common site for Crohn's)
• History of anal fissure - a well-known extraintestinal/perianal manifestation of Crohn's disease
• Constipation can occur in Crohn's (stricturing disease causing obstructive symptoms)
• RIF pain for 3 days

• Bowel wall thickening with preserved stratification ("target sign" or "pseudokidney sign")
• Increased Doppler flow (hyperaemia)
• Creeping mesenteric fat
• Enlarged mesenteric lymph nodes
• Terminal ileum most commonly affected

2. Ileocaecal Tuberculosis - MUST EXCLUDE (especially in endemic regions)

• Affects the terminal ileum and ileocaecal junction - exactly the RIF
• Causes bowel wall thickening and narrowing, closely mimics Crohn's
• Bailey & Love's states: "The infection establishes itself in lymphoid follicles, causing thickening of the intestinal wall and narrowing of the lumen. There is early involvement of regional lymph nodes which may caseate."
• The differential diagnosis of ileocaecal TB includes Crohn's disease, appendix mass, lymphoma, carcinoma of the caecum
• Distinguishing features from Crohn's: enlarged low-attenuation mesenteric nodes with peripheral ring enhancement (on CT), no fistulae/abscesses, constitutional symptoms (fever, weight loss, night sweats)

3. Mesenteric Lymphadenitis (Yersinia / Viral)

• Common in young males
• Yersinia enterocolitica specifically causes terminal ileitis with inflamed bowel loops, mimicking Crohn's and appendicitis
• Associated with enlarged mesenteric lymph nodes on USS
• Usually self-limiting (1-3 weeks)
• History of diarrhoea or recent URTI supports this

4. Adhesion-related Partial Bowel Obstruction with Secondary Inflammation

• Post-appendicectomy adhesions can cause intermittent partial obstruction of the terminal ileum
• Partial obstruction leads to bowel wall oedema (appearing "inflamed" on USS)
• However, this would typically show proximal dilatation of small bowel loops

5. Stump Appendicitis

• Inflamed bowel in the RIF could represent peri-stump inflammation
• The stump itself may not be well visualised on USS
• CT would be more definitive

How to Differentiate Crohn's from Ileocaecal TB on USS/Imaging

Next Steps - Investigation Plan

Immediate

Definitive

Critical Warning: DO NOT Start Steroids Without Ruling Out TB

Summary

• Anal fissure (perianal Crohn's feature)
• Constipation (possible structuring/obstructive Crohn's)
• RIF pain

Bailey and Love's Surgery, p. 1330: "In ileocaecal tuberculosis, the terminal ileum is narrowed and thickened... the differential diagnosis is that of an appendix mass, lymphoma, carcinoma of the caecum, CD, tuberculosis or actinomycosis." Grainger & Allison's Diagnostic Radiology: "CT shows bowel wall thickening with homogeneous attenuation and lack of mural stratification [in TB]... the presence of enlarged, low-attenuation mesenteric nodes with enhancing peripheral rings are important clues in differentiating between abdominal TB and CD."