If you can't feel it in a thin child go for laparoscopy. If the child is chubby, ultrasound should be done 1st.

In a case with non plapable undescended testis, best would be an examination under anesthesia & proceed to Lap, after informed consent. US / MR in exceptional cases like child obese / difficult to examine. In view of operator dependent examination, US is best not done, atleast to avoid misinterpretation. There have been instances when the referring Paediatrician does an US with a report of testis present, but on exploration only a nubbin being present, leaving the Surgeon 'defenceless'. In the hands of an expert Paediatric Sonologist may be chances of misinterpretation are minimum.

In a child with non-palpable testis, I agree with Krishna Govindarajan's approach. The value of USG in non-palpable testis is no higher than physical examination. There is a good paper on this subject:

Imaging studies for non-palpable testis: Are they at all required?

Pradhan MR, Ansari MS. Indian J Urol. 2012 Apr;28(2):227-9.

Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22919150/

I also completely agree with approach as suggested by DR Krishna.

In addition laparoscopy may help identifying fusion anomalies (See below)

which when identified can help formulate realistic expectations with regards to fertility especially when it is a bilateral affliction. These are never picked up by USG.

Eur J Pediatr Surg 2009; 19(2): 108-109

DOI: 10.1055/s-2008-1039194

© Georg Thieme Verlag KG Stuttgart · New York

Failure of Fusion of Epididymis and Testis: A Rare Laparoscopic Finding

M. A. El Gohary1

1Department of Pediatric Surgery, Mafraq Hospital, Abu Dhabi, United Arab Emirates

Abstract

A case of complete separation between an abdominal testis and the epididymis discovered during diagnostic laparoscopy for impalpable testis is presented. A 13-year-old boy with impalpable testis underwent diagnostic laparoscopy for impalpable testis. The vas on the left side was seen entering a closed internal ring while a small testis was found completely separated and medial to the internal ring.

Ultrasound clearly has no place in diagnosing of non palpable testis. If you find something you cannot differentiate from lymph nodes, or others, if you do not find anything you do not know more than before the investigation. But a positive finding "forces" you somehow to explore, from the risk of being sued later on for ignoring the finding. A lot of literature since more than 20years exists on this topic, as already pointed out by David Thomas, and the overall message seems to be laparoscopy is the method of choice in non palpable testis for diagnosis and consecutive treatment.