Experience with several incarcerations that resulted in emergent surgery for children with known indirect inguinal hernias prompted this review to determine if there is an optimal time after hernia diagnosis during which elective repair should be undertaken to avoid incarceration. Over a 30 month period, 228 children less than 10 years of age underwent 303 indirect inguinal hernia repairs. They were analyzed for age, sex, interval between diagnosis and repair, predisposing conditions, major complications, and length of hospitalization. Excluded were 21 children who presented with incarceration of a previously undiagnosed indirect inguinal hernia that required operative reduction, 13 children with conditions predisposing to indirect inguinal hernia, and 53 children for whom the interval between diagnosis and repair was unknown, leaving a study group of 141 children who underwent 190 indirect inguinal hernia repairs. Nearly 13% (18 of 141) of the children developed incarcerated hernia prior to elective repair. Compared to children who underwent repair of a reducible indirect inguinal hernia, those with incarceration were more likely (p less than 0.05): 1) to have major complications (11% vs 0.6%), 2) to have a shorter interval between diagnosis and repair (26 vs 49 days), 3) to be younger (7.5 vs 25.6 mos), and 4) to require greater than 24 hours of hospitalization. Had children with reducible incarcerated indirect inguinal hernia been hospitalized and undergone repair 24 to 48 hours later, 83% of subsequent incarcerations would have been prevented. Furthermore, this experience supports the recommendation that for healthy children less than 10 years of age, indirect inguinal hernia repair should be performed on a semi-elective basis within 7 days of diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

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and the Department of Surgery, Dearborn Veterans Hospital, Dearborn, M k h .The search for ideal contrast media for radiodiagnostic studies has extended over many decades. Although many serviceable contrast media have been developed and are now in clinical use, all the properties of an ideal contrast medium have never been captured in a single preparation. I t is well known that each of the available contrast media has particular, though not necessarily prohibitive, disadvantages. This paper will describe briefly the application of polyvalent-metal chelates as contrast media in bronchography and angiocardiography in anesthetized dogs. Because certain chemical and physical properties are possessed by heavymetal chelates, this group of compounds may be studied profitably for potential use as contrast media. Literally, scores of compounds in this category remain to be synthesized and investigated.Sa~eika,*-~ in 1954, was the first investigator to report the use of polyvalentmetal chelates as contrast media. He used Pb-ethylenediaminetetraacetate (PbEDTA) in a variety of experimental animals and, later, in human beings4 Following this lead, in 1956, Migliorini and Toddei5 in Italy and Shapiro6 in this country published their observations on the use of PbEDTA as a contrast medium in animals. These authors all have been hopefully impressed with this use of this chelate.Chelation has been defined as a reversible reaction between a polyvalent metallic ion and a polyaminocarboxylic acid to form, within the molecule, one or more heterocyclic ring structures, incorporating the metallic ion by both electrovalent and covalent bonds. The metallic ion thus becomes firmly bound and unavailable for chemical or physiological activity. The reaction product is called a chelate, a name derived from the Greek chele, meaning claw, which is descriptive of the "clawlike" structure of the chelate. The physical and chemical properties possessed by some heavy-metal chelates include (1) excellent radiopacity, (2) crystalline structure, ( 3 ) solubility in water, (4) physiological inertness within dosage limits, and (5) rapidity of excretion through the genitourinary tract and, to a lesser degree, the gastrointestinal tract.The literature dealing with the theoretical aspects of chelation chemistry is enormous. However, a brief statement of some pertinent basic concepts will be helpful. The reversible reaction of a chelate and the polyvalent metal is depicted :The equilibrium constant, K , , is a measure of the extent to which chelation