Can a 40-year-old male with right-sided abdominal pain radiating to the lower back be experiencing pain solely due to a muscle spasm?

Can Right-Sided Abdominal Pain Radiating to the Lower Back Be Solely a Muscle Spasm?

While muscle spasm can cause right-sided abdominal pain radiating to the lower back, this presentation in a 40-year-old male requires systematic exclusion of serious intra-abdominal and spinal pathology before attributing symptoms solely to musculoskeletal causes. 1

Critical Red Flags to Exclude First

Before considering muscle spasm as the sole diagnosis, you must immediately assess for:

• Appendicitis: The most common surgical pathology causing right lower quadrant pain, with clinical examination alone having an unacceptably high 25% negative appendectomy rate 1
• Renal pathology: Kidney stones or pyelonephritis commonly present with flank pain radiating to the lower back 1
• Spinal nerve root compression: Radiculopathy from lumbar disc herniation can mimic abdominal wall pain 1, 2
• Serious spinal conditions: Vertebral infection, fracture, or cauda equina syndrome if any neurologic symptoms are present 1, 2

Diagnostic Approach for Abdominal Wall Pain

Carnett's Test is the key clinical maneuver to differentiate muscle spasm from visceral pathology:

• Have the patient tense their abdominal muscles by lifting their head and shoulders off the examination table 3
• Positive test: Pain stays the same or worsens = suggests abdominal wall origin 3
• Negative test: Pain decreases = suggests visceral origin 3

Localized tender point at the lateral edge of the rectus abdominis that worsens with position changes strongly suggests anterior cutaneous nerve entrapment syndrome, the most commonly missed cause of abdominal wall pain 3

When Muscle Spasm Is the Likely Diagnosis

Muscle spasm (rectus syndrome or iliopsoas muscle syndrome) should be considered when:

• Pain is localized to a small tender spot without diffuse abdominal tenderness 3, 4
• Positive Carnett's test 3
• Pain triggered by specific movements or repetitive exercise 5, 6
• No fever, weight loss, or constitutional symptoms 1
• No urinary, bowel, or neurologic symptoms 1, 2
• Iliopsoas muscle involvement can cause pain in the groin, anterior thigh, and lower back on the affected side 6

Confirmatory Testing

Diagnostic local anesthetic injection provides both diagnosis and treatment:

• 50% or greater pain improvement after injection confirms abdominal wall origin 3
• Overall response rate of 70-99% for anterior cutaneous nerve entrapment syndrome 3
• Point-of-care ultrasonography can guide injections and rule out other abdominal wall pathologies 3

Critical Pitfall to Avoid

Do not assume muscle spasm without excluding serious pathology. Imaging remains the diagnostic mainstay for right-sided abdominal pain when clinical examination is equivocal 1. The painful spasm of the iliopsoas muscle can mimic diseases of abdominal and pelvic organs, and organic diseases (abscess, hematoma, tumor) must be excluded first 6.

Treatment Algorithm If Muscle Spasm Is Confirmed

1. Reassurance and patient education about the benign nature of the condition 3
2. Local anesthetic and corticosteroid injection for anterior cutaneous nerve entrapment syndrome 3
3. Skeletal muscle relaxants (cyclobenzaprine 5-10 mg three times daily) for acute muscle spasm, used only for short periods (2-3 weeks) 1, 7
4. Physical therapy focusing on stretching and strengthening 6
5. Surgical neurectomy for refractory cases requiring more than two injections 3

The key message: Right-sided abdominal pain radiating to the lower back can be from muscle spasm, but only after systematic exclusion of appendicitis, renal pathology, and spinal conditions through appropriate clinical examination and selective imaging when indicated. 1