Hydroceles predominantly occur in males and are rare in females. They are common in male infants and children and in many cases are associated with an indirect inguinal hernia.[5]Kapur P, Caty MG, Glick PL. Pediatric hernias and hydroceles. Pediatr Clin North Am. 1998 Aug;45(4):773-89.
http://www.ncbi.nlm.nih.gov/pubmed/9728185?tool=bestpractice.com
Approximately 1% to 3% of full-term infants have a hydrocele or hernia.[6]Baskin LS, Kogan BA. Hydrocele/hernia. In: Gonzales ET, Bauer SB, eds. Pediatric urology practice. Philadelphia, PA: Lippincott, Williams & Wilkins; 1999:649-53. Hydroceles are more prevalent in premature infants and in infants whose testes descend relatively late. Autopsy findings suggest patent processus vaginalis is present in 80% to 94% of infants and 15% to 30% of adults.[7]Skoog SJ. Benign and malignant pediatric scrotal masses. Urol Clin North Am. 1997 Oct;44(5):1229-50.
http://www.ncbi.nlm.nih.gov/pubmed/9326960?tool=bestpractice.com
[8]Barthold JS, Kass EJ. Abnormalities of the penis and scrotum. In: Belman AB, King LR, Kramer SA, eds. Guide to clinical pediatric urology. London: Martin Dunitz; 2002:267-98.[9]Rowe MI, Copelson LW, Clatworthy HW. The patent processus vaginalis and the inguinal hernia. J Pediatr Surg. 1969 Feb;4(1):102-7.
http://www.ncbi.nlm.nih.gov/pubmed/5779274?tool=bestpractice.com
[10]Bronsther B, Abrams MW, Elboim C. Inguinal hernias in children - a study of 1,000 cases and a review of the literature. J Am Med Womens Assoc. 1972 Oct;27(10):522-5.
http://www.ncbi.nlm.nih.gov/pubmed/4342346?tool=bestpractice.com
In the presence of a patent processus vaginalis, the incidence of a contralateral patent processus vaginalis has been found to be 15% to 22%.[11]Schneck FX, Bellinger MF. Abnormalities of testis and scrotum and their surgical management. In: Wein AJ, Kavoussi LR, Novick AC, et al, eds. Campbell-Walsh urology. 9th ed. Philadelphia, PA: WB Saunders; 2007:3761-98. In the majority of cases, the processus vaginalis closes within the first year of life and so the incidence of hydrocele decreases.[7]Skoog SJ. Benign and malignant pediatric scrotal masses. Urol Clin North Am. 1997 Oct;44(5):1229-50.
http://www.ncbi.nlm.nih.gov/pubmed/9326960?tool=bestpractice.com
[8]Barthold JS, Kass EJ. Abnormalities of the penis and scrotum. In: Belman AB, King LR, Kramer SA, eds. Guide to clinical pediatric urology. London: Martin Dunitz; 2002:267-98.[9]Rowe MI, Copelson LW, Clatworthy HW. The patent processus vaginalis and the inguinal hernia. J Pediatr Surg. 1969 Feb;4(1):102-7.
http://www.ncbi.nlm.nih.gov/pubmed/5779274?tool=bestpractice.com
[10]Bronsther B, Abrams MW, Elboim C. Inguinal hernias in children - a study of 1,000 cases and a review of the literature. J Am Med Womens Assoc. 1972 Oct;27(10):522-5.
http://www.ncbi.nlm.nih.gov/pubmed/4342346?tool=bestpractice.com
Intrauterine exposure to polybrominated biphenyl, a brominated flame retardant and endocrine disruptor, has been found to increase the risk of hydrocele/hernia.[12]Small CM, DeCaro JJ, Terrell ML, et al. Maternal exposure to a brominated flame retardant and genitourinary conditions in male offspring. Environ Health Perspect. 2009 Jul;117(7):1175-9.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717147
http://www.ncbi.nlm.nih.gov/pubmed/19654930?tool=bestpractice.com
In boys presenting with a painless scrotal mass 15% to 50% have a hydrocele.[13]Metcalfe PD, Farivar-Mohseni H, Farhat W, et al. Pediatric testicular tumors: contemporary incidence and efficacy of testicular preserving surgery. J Urol. 2003 Dec;170(6 pt 1):2412-5; discussion 2415-6.
http://www.ncbi.nlm.nih.gov/pubmed/14634440?tool=bestpractice.com
[14]Ahmed HU, Arya M, Muneer A, et al. Testicular and paratesticular tumours in the prepubertal population. Lancet Oncol. 2010 May;11(5):476-83.
http://www.ncbi.nlm.nih.gov/pubmed/20434716?tool=bestpractice.com
The incidence in adult men is not known. Up to 20% of patients develop a hydrocele after varicocelectomy.[15]Al-Kandari AM, Shabaan H, Ibrahim HM, et al. Comparison of outcomes of different varicocelectomy techniques: open inguinal, laparoscopic, and subinguinal microscopic varicocelectomy: a randomized clinical trial. Urology. 2007 Mar;69(3):417-20.
http://www.ncbi.nlm.nih.gov/pubmed/17382134?tool=bestpractice.com
However, with some highly specialised microsurgical techniques, the occurrence rate may be decreased to less than 1%.[15]Al-Kandari AM, Shabaan H, Ibrahim HM, et al. Comparison of outcomes of different varicocelectomy techniques: open inguinal, laparoscopic, and subinguinal microscopic varicocelectomy: a randomized clinical trial. Urology. 2007 Mar;69(3):417-20.
http://www.ncbi.nlm.nih.gov/pubmed/17382134?tool=bestpractice.com
[16]Esposito C, Valla JS, Najmaldin A, et al. Incidence and management of hydrocele following varicocele surgery in children. J Urol. 2004 Mar;171(3):1271-3.
http://www.ncbi.nlm.nih.gov/pubmed/14767329?tool=bestpractice.com
[17]Lipshultz LI, Thomas AJ, Khera M. Surgical management of male infertility. In: Wein AJ, Kavoussi LR, Novick AC, et al, eds. Campbell-Walsh urology. 9th ed. Philadelphia, PA: WB Saunders; 2007:665. Approximately 10% of testicular malignancies are thought to present with hydroceles.[7]Skoog SJ. Benign and malignant pediatric scrotal masses. Urol Clin North Am. 1997 Oct;44(5):1229-50.
http://www.ncbi.nlm.nih.gov/pubmed/9326960?tool=bestpractice.com
Filariasis is common in many countries worldwide and is often associated with hydroceles that occur as a result of lymphatic obstruction.[18]Streit T, Lafontant JG. Eliminating lymphatic filariasis: a view from the field. Ann N Y Acad Sci. 2008;1136:53-63.
https://nyaspubs.onlinelibrary.wiley.com/doi/10.1196/annals.1425.036
http://www.ncbi.nlm.nih.gov/pubmed/18579875?tool=bestpractice.com