In a 15‑year‑old male with persistent left lower‑quadrant abdominal tenderness and bruising, right‑sided back pain radiating to the ribs, and new left great‑toe stabbing pain with tingling after a recent appendectomy, what imaging studies and medical management are indicated?

Immediate CT Abdomen and Pelvis with IV Contrast is Indicated

This 15-year-old requires urgent CT imaging of the abdomen and pelvis with IV contrast to evaluate for post-operative complications, intra-abdominal pathology causing the unexplained bruising and persistent pain, and to rule out vascular or hemorrhagic complications.

Clinical Red Flags Requiring Immediate Advanced Imaging

This presentation contains multiple concerning features that mandate CT evaluation:

• Unexplained bruising in the left lower abdomen without trauma history suggests possible spontaneous hemorrhage (rectus sheath hematoma, retroperitoneal bleeding, or vascular injury) 1, 2
• Persistent abdominal pain 3 months post-appendectomy raises concern for post-operative complications including abscess, adhesions, or missed pathology 1
• Diffuse abdominal tenderness with maximal left lower quadrant pain requires evaluation for complicated intra-abdominal infection, bowel pathology, or inflammatory processes 1
• New neurologic symptoms (left leg pain with tingling and cold sensation) could indicate vascular compromise or referred pain from retroperitoneal pathology 2

Recommended Imaging Protocol

CT abdomen and pelvis with IV contrast is the preferred initial imaging modality for evaluating left lower quadrant pain with this constellation of symptoms 1. The ACR Appropriateness Criteria specifically recommend CT as the most useful examination for left lower quadrant pain because it:

• Accurately detects small quantities of extraluminal air indicating perforation 1
• Identifies spontaneous hemorrhage in the retroperitoneum or rectus sheath 2
• Evaluates for post-operative complications including abscess formation 1
• Assesses vascular structures and can detect thrombosis or bleeding 1, 2

IV contrast is usually appropriate for CT in this clinical scenario to enhance diagnostic accuracy, though CT without IV contrast also maintains high diagnostic accuracy if contrast is contraindicated 1.

Differential Diagnosis Requiring Urgent Evaluation

The unexplained bruising is the most alarming finding and must be investigated for:

• Spontaneous rectus sheath hematoma or retroperitoneal hemorrhage 2
• Post-operative complications including occult bleeding or abscess formation 1
• Vascular pathology causing both abdominal symptoms and lower extremity neurologic changes 2
• Inflammatory bowel disease or other colonic pathology 1, 2

Additional Considerations for the Right-Sided Back/Rib Pain

While the abdominal findings take priority, the right-sided back pain radiating to ribs could represent:

• Painful rib syndrome (slipping rib syndrome), which presents with pain in lower chest/upper abdomen, tender spot on costal margin, and reproduction of pain with palpation 3, 4
• Referred pain from intra-abdominal pathology that will be evaluated on the CT 1
• Musculoskeletal pain, though this diagnosis should only be accepted after excluding serious pathology 3

The "hooking maneuver" (pulling anteriorly on the costal margin) can reproduce pain in slipping rib syndrome, but this musculoskeletal diagnosis should not distract from the urgent need to evaluate the abdominal bruising and pain 4.

Management Algorithm

1. Order CT abdomen/pelvis with IV contrast immediately 1
2. Hold muscle relaxants until serious pathology is excluded, as they may mask worsening symptoms 1
3. Maintain NPO status pending imaging results in case surgical intervention is needed 1
4. Obtain complete blood count to assess for anemia from occult bleeding
5. Consider coagulation studies given unexplained bruising

Critical Pitfall to Avoid

Do not attribute all symptoms to musculoskeletal pain or dismiss the bruising as insignificant. The combination of unexplained bruising, post-operative status, and progressive symptoms represents a potentially serious intra-abdominal process requiring definitive imaging evaluation 1, 2. The normal neurovascular exam of the lower extremities does not exclude retroperitoneal or vascular pathology that could be causing referred symptoms 2.

Regarding the Epinephrine Auto-Injector

The epinephrine auto-injector refill request is appropriate and should be provided, but is secondary to the urgent evaluation of the abdominal findings.