In a 79‑year‑old man presenting to the emergency department with left flank, left lower‑quadrant, and anterior midline scrotal pain, no dysuria or fever, mild leukocytosis, and a contrast‑enhanced CT showing mild uncomplicated sigmoid diverticulitis, a chronic right posterolateral bladder diverticulum, right‑sided small renal stones, a normal left kidney, and a penile prosthesis reservoir in the right pelvis, what is the differential diagnosis for his pain and what additional evaluation should be performed while awaiting scrotal ultrasound results?

Differential Diagnosis and Additional Evaluation

Primary Diagnosis: Mild Uncomplicated Sigmoid Diverticulitis

The CT findings of mild uncomplicated sigmoid diverticulitis are the most likely source of this patient's left lower quadrant pain, and the scrotal pain is likely referred or represents a separate benign process unrelated to the diverticulitis. 1

Key Supporting Evidence

• The CT explicitly identifies "suspect mild acute uncomplicated diverticulitis involving a diverticulum along the superior margin of the proximal mid sigmoid colon" with moderate-to-severe diverticulosis 1
• Left lower quadrant pain with diverticulitis is the most common cause in adults over 50 years, and this patient is 79 years old 1
• The absence of fever, normal WBC (10.9), and lack of peritoneal signs support uncomplicated disease 1
• CT with IV contrast has 98% diagnostic accuracy for diverticulitis 1

Complete Differential Diagnosis

1. Sigmoid Diverticulitis (Primary Diagnosis)

• Uncomplicated diverticulitis is confirmed by CT showing bowel wall thickening and pericolonic inflammation without abscess, perforation, or fistula 1
• The patient's age (79 years), left-sided pain, and CT findings make this the leading diagnosis 1
• Mild leukocytosis (10.9) is consistent with mild inflammation 1

2. Colovesical Fistula (Critical to Exclude)

• The CT shows a prominent 5 cm bladder diverticulum and sigmoid diverticulitis in close proximity 2
• Pneumaturia and fecaluria are pathognomonic signs that must be specifically asked about, as colovesical fistula is an uncommon but serious complication of diverticulitis 2
• The patient denies dysuria, but this does not exclude fistula 2
• The bladder diverticulum suggests chronic outlet obstruction, which may predispose to fistula formation 1

3. Scrotal Pain Etiologies

A. Epididymitis/Epididymo-orchitis (Most Likely Scrotal Cause)

• This is the most common cause of scrotal pain in adults, representing approximately 600,000 cases annually in the United States 3
• Gradual onset and anterior midline location are consistent with epididymitis 3
• The absence of dysuria does not exclude this diagnosis 3
• Ultrasound will show enlarged epididymis with increased blood flow on color Doppler 3

B. Testicular Torsion (Must Be Excluded Urgently)

• Although rare in patients over 35 years, testicular torsion remains a surgical emergency requiring intervention within 6-8 hours 3
• The 1-year history of non-use of the penile pump makes mechanical torsion from the device unlikely 3
• Ultrasound will show decreased or absent blood flow if torsion is present 3

C. Referred Pain from Diverticulitis

• Sigmoid diverticulitis can present with atypical referred pain patterns 4
• The left flank and LLQ pain radiating to the scrotum may represent referred pain along shared nerve pathways 4

D. Penile Prosthesis Complication

• Although the patient states no recent use and no prior issues, infection or mechanical complication of the reservoir (located in right pelvis per CT) must be considered 1
• The anterior midline scrotal pain location away from the pump base makes pump-related pathology less likely 1

4. Renal Stone Disease (Partially Explains Flank Pain)

• CT shows "multiple punctate right renal stones measuring up to 3-4 mm" 1
• No left-sided stones, no hydronephrosis, and no ureteral stone identified 1
• The right-sided stones are non-obstructing and unlikely to cause left flank pain 1
• History of kidney stones makes this a consideration, but CT findings do not support active stone disease as the cause of current symptoms 1

5. Bladder Outlet Obstruction

• The "lobulated/slightly trabeculated appearing bladder with a prominent 5 cm widemouth diverticulum" suggests chronic bladder outlet obstruction 1
• This is typically a chronic process and unlikely to cause acute pain 1
• May contribute to urinary symptoms if present 1

6. Less Likely Diagnoses to Consider

• Pyelonephritis: Ruled out by CT showing "no evidence of acute pyelonephritis" 1
• Appendicitis: Ruled out by CT showing "no evidence of appendicitis" 1
• Abdominal aortic aneurysm: CT shows "mild-to-moderate atherosclerosis, no aneurysm" 1
• Colon cancer: Must be considered in elderly patients with diverticulitis; pericolonic lymphadenopathy >1 cm would suggest cancer rather than diverticulitis 1

Additional Evaluation Beyond Ultrasound

Immediate Additional Testing

1. Detailed Urinary Symptom History

   • Specifically ask about pneumaturia (air in urine) and fecaluria (fecal material in urine), which are pathognomonic for colovesical fistula 2
   • Ask about recurrent urinary tract infections, which may indicate fistula 2
   • Clarify any changes in urinary stream or hesitancy related to bladder outlet obstruction 1

2. Urinalysis with Microscopy and Culture

   • Essential to evaluate for urinary tract infection, which may explain scrotal pain if epididymitis is present 3
   • Presence of fecal material or mixed enteric organisms suggests colovesical fistula 2
   • Pyuria without bacteriuria may indicate epididymitis 3

3. C-Reactive Protein (CRP)

   • CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity 5
   • Helps risk-stratify the diverticulitis and guide treatment decisions 5
   • CRP >50 mg/L combined with left lower quadrant tenderness and absence of vomiting has 97% accuracy for diverticulitis 1

4. Complete Blood Count with Differential

   • WBC 10.9 is mildly elevated; a left shift >75% suggests bacterial infection 1
   • Helps differentiate inflammatory from infectious processes 1

5. Scrotal Ultrasound with Color Doppler (Already Pending)

   • This is the essential first-line imaging for scrotal pain with sensitivity of 69-96.8% and specificity of 87-100% for testicular torsion 3
   • Will differentiate epididymitis (increased flow) from torsion (decreased/absent flow) 3
   • Should include grayscale examination, color Doppler assessment of testicular perfusion, and power Doppler 3
   • Use contralateral testicle as internal control 3

Conditional Additional Testing

1. Cystoscopy (If Fistula Suspected)

   • If pneumaturia or fecaluria is present, cystoscopy can directly visualize the fistula tract 2
   • The primary aim is to confirm the fistula and plan surgical repair 2

2. Colonoscopy (Selective Indication)

   • NOT routinely indicated after CT-confirmed uncomplicated diverticulitis except for age-appropriate screening not yet performed 1
   • IS indicated if CT shows abnormal pericolonic lymph nodes >1 cm, luminal mass, abscess, perforation, or fistula 1
   • Given the bladder diverticulum and concern for possible fistula, colonoscopy may be warranted after acute inflammation resolves 1

3. Repeat CT Abdomen/Pelvis with IV Contrast

   • Indicated if symptoms persist >2-3 days despite conservative management 1
   • Indicated if fever develops, pain worsens, or signs of peritonitis appear 1
   • Not immediately necessary given current stable presentation 1

4. Urology Consultation

   • Immediate consultation if scrotal ultrasound shows testicular torsion (surgical emergency within 6-8 hours) 3
   • Routine consultation for evaluation of bladder outlet obstruction and bladder diverticulum 1
   • Consultation for penile prosthesis evaluation if device-related complication suspected 1

Management Algorithm Based on Findings

For Uncomplicated Diverticulitis (Current Presentation)

Conservative management WITHOUT antibiotics is appropriate for this immunocompetent patient with uncomplicated diverticulitis. 1

• Clear liquid diet with advancement as tolerated 1
• Oral analgesics for pain control 1
• Outpatient management is appropriate given absence of fever, peritoneal signs, and ability to tolerate oral intake 1

Antibiotics are NOT indicated in immunocompetent patients with uncomplicated diverticulitis, as they do not improve outcomes and promote resistance 1

Antibiotics WOULD be indicated only if:

• Patient were immunocompromised or critically ill 1
• Fever develops 1
• Signs of complicated diverticulitis appear (abscess, perforation) 1
• If antibiotics are needed: Ertapenem 1 g q24h or Eravacycline 1 mg/kg q12h for maximum 7 days 1

For Scrotal Pain (Pending Ultrasound)

If ultrasound shows epididymitis:

• Bed rest, scrotal elevation, analgesics 3
• Antibiotics based on age and risk factors 3
• Follow-up in 48-72 hours to ensure improvement 3

If ultrasound shows testicular torsion:

• Immediate urological consultation and surgical exploration within 6-8 hours 3
• This is a surgical emergency despite the patient's age 3

If ultrasound is normal but clinical suspicion remains high:

• Consider repeat imaging or surgical exploration, as false-negative Doppler occurs in up to 30% of cases 3
• Clinical judgment supersedes imaging when torsion is suspected 3

Critical Pitfalls to Avoid

1. Do not assume scrotal pain is benign in elderly patients—testicular torsion, though rare over age 35, remains a surgical emergency 3

2. Do not miss colovesical fistula—specifically ask about pneumaturia and fecaluria, as this complication requires surgical repair 2

3. Do not prescribe antibiotics for uncomplicated diverticulitis in immunocompetent patients—this increases resistance without improving outcomes 1

4. Do not delay scrotal ultrasound—testicular viability is compromised if torsion is not treated within 6-8 hours 3

5. Do not rely on clinical examination alone—misdiagnosis rates for diverticulitis are 34-68% without imaging 1

6. Do not order routine colonoscopy after uncomplicated diverticulitis—it is only indicated for age-appropriate screening or if CT shows concerning features 1

7. Do not assume the penile prosthesis is unrelated—although the patient reports no recent use, device-related complications must be considered 1