What is the diagnosis for a 5-year-old boy with sudden onset right groin pain that has improved but remains tender to the touch (TTP) in the mid inguinal canal, without evidence of a hernia, and non-palpable testes on scrotal examination?

Diagnosis: Torsion of Undescended Testis in the Inguinal Canal

The most likely diagnosis is torsion of an undescended testis located within the inguinal canal, which presents as acute groin pain with a tender mass in the mid-inguinal canal and non-palpable testes in the scrotum. 1

Clinical Reasoning

This 5-year-old boy's presentation is pathognomonic for this specific condition:

• Sudden onset groin pain that has improved suggests spontaneous detorsion or partial torsion of an undescended testis, which can present with intermittent symptoms 2
• Tenderness in the mid-inguinal canal corresponds to the location of an undescended testis undergoing torsion 1
• Non-palpable testes in the scrotum confirms cryptorchidism, which is the underlying anatomic abnormality 3
• No hernia visualized helps exclude inguinal hernia as the primary diagnosis 1

Why This Diagnosis Takes Priority

• Torsion of undescended testis is a surgical emergency requiring intervention within 6-8 hours to prevent permanent testicular loss, even though symptoms have improved 2
• The cryptorchid testis has inherent increased risk of torsion compared to normally descended testes 3
• Spontaneous detorsion can occur, explaining the improvement in pain, but this does not eliminate the need for urgent surgical intervention as re-torsion is highly likely 2

Immediate Management Algorithm

Step 1: Urgent Doppler Ultrasound

• Obtain Duplex Doppler ultrasound of the inguinal canal and scrotum to confirm the diagnosis 3
• Look for the "whirlpool sign" of twisted spermatic cord with 96% sensitivity 2
• Assess testicular blood flow - decreased or absent flow confirms torsion 2
• Power Doppler is particularly useful in prepubertal boys who have normally reduced intratesticular blood flow 2

Step 2: Immediate Urological Consultation

• Do not delay surgical exploration even if ultrasound findings are equivocal, as false-negative Doppler evaluations occur in 30% or more of cases 2
• Clinical suspicion should drive management when imaging is inconclusive 2

Step 3: Surgical Intervention

• Surgical exploration must occur urgently, ideally within 6-8 hours of initial symptom onset (not current presentation) 2
• The procedure should include bilateral orchiopexy to prevent contralateral torsion, as the bell-clapper deformity is often bilateral 2
• If the testis is viable after detorsion, perform orchiopexy to bring it into the scrotum 3
• If the testis is necrotic and the contralateral testis is normal, orchiectomy may be considered 3

Critical Pitfalls to Avoid

• Do not be falsely reassured by symptom improvement - spontaneous detorsion does not eliminate the need for urgent intervention 2
• Do not assume absence of scrotal findings rules out testicular pathology - the undescended testis is located in the inguinal canal, not the scrotum 1
• Do not delay imaging or consultation because the child appears comfortable - testicular viability depends on time from initial symptom onset 2
• Do not mistake this for simple inguinal hernia or lymphadenopathy - non-palpable testes is the key distinguishing feature 1

Long-Term Considerations

• Cryptorchidism carries 2.75-fold increased risk of testicular malignancy, which is reduced by prepubertal orchiopexy 3
• Fertility may be compromised even with successful orchiopexy, requiring long-term counseling 3
• Teach testicular self-examination after puberty for early cancer detection 3