during a period of 25 years , the first author operated on 42 patients with hydroceles . all of these patients were prospectively screened for calculous material in the tunica vaginalis testis . two patients were found to have scrotal calculi ( calculi in the hydrocele fluid ) , accounting for an incidence rate of 4.8% . analyses of the hydrocele stones were performed with infrared spectroscopy ( fourier transform ( ft)-ir spectrometer spectrum bx , fa . perkin elmer , germany ) based on the atlas of infrared spectra for the analysis of concrements . a 20-year - old white male with a small hydrocele and a palpable mass suspicious of testicular cancer on the right side underwent inguinal exploration . frozen section pathology showed only old scars on the tunica albuginea testis . in the 10 cc clear , amber , nonmalodorous hydrocele fluid , a 2 g rough , white stone was found ( fig . 1a ) that was not attached to the tunica vaginalis testis . infrared spectroscopy revealed 100% carbonate apatite ( fig . an 80-year - old patient was operated on for an asymptomatic right hydrocele . in the 300 cc clear , amber , non - malodorous hydrocele fluid between the tunica vaginalis testis visceralis and parietalis , an 11 g bizarre - shaped , brown stone without attachment to the tunica vaginalis was found ( fig . a 20-year - old white male with a small hydrocele and a palpable mass suspicious of testicular cancer on the right side underwent inguinal exploration . frozen section pathology showed only old scars on the tunica albuginea testis . in the 10 cc clear , amber , nonmalodorous hydrocele fluid , a 2 g rough , white stone was found ( fig . 1a ) that was not attached to the tunica vaginalis testis . infrared spectroscopy revealed 100% carbonate apatite ( fig . an 80-year - old patient was operated on for an asymptomatic right hydrocele . in the 300 cc clear , amber , non - malodorous hydrocele fluid between the tunica vaginalis testis visceralis and parietalis , an 11 g bizarre - shaped , brown stone without attachment to the tunica vaginalis was found ( fig . single or multiple scrotal calculi ( hydrocele calculi , hydrocele stones , or calculi in hydrocele fluid ) are freely moving concretions that lie in the space between the tunicae lining the scrotum and the testicles . they are much more common in clinical practice than what the literature would suggest , because most surgeons do not report them . often , they are not even turned in to pathology and therefore are not described in the reports . these calcifications are believed to originate either as fibrinous deposits in the tunica vaginalis testis after trauma or inflammation , as desquamated endothelial cells , or as remnants of the appendix testis or appendix epididymidis that have undergone torsion and become freely movable [ 2 - 4 ] . hussein et al mention parasites , especially filarial worms , as one of the causes of calculi in hydroceles . frauscher et al found an incidence of scrotal calculi of 81% in extreme mountain bikers in addition to epididymal calcifications in 40% and testicular calcifications in 32% compared with 0% in a control group . snchez merino et al found 3 calculi in 2 patients with hydrocele that were white and smooth , but turned yellow and rough after removal . scanning electron microscopy and x - ray dispersion studies showed a center comprised of hydroxyapatite and white organic matter and an exterior of yellow organic matter in all 3 stones . the mineral portion of the center of the 6 mm calculus and one of the 2 mm calculi was composed of 33% phosphorus and 67% calcium ; the other 2 mm calculus contained 32% phosphorus and 68% calcium by x - ray dispersion analysis . that matches well with the 100% carbonate apatite [ ca10(po4,co3)6(oh , co3)2 ] in our patients ' hydrocele stones found by infrared spectroscopy . to our knowledge , this method was used for this purpose for the first time in this study . carbonate apatite can precipitate in an alkaline milieu . during infection , extreme mountain biking and other trauma or torsion of the appendix testis , respectively , epididymis bleeding or necrosis leads to the deposit of organic matter . in the presence of high oversaturation of calcium phosphates and the absence of crystallization inhibitors in an alkaline milieu a scrotal calculus was first described during surgery in 1934 as a " fibrinoid loose body " or " scrotal pearl " ( cited by ) . since chatterjee ( 1975 ) , whereas 4.7% of all scrotal tissues contain calcifications , this rate is 1% for tunica vaginalis calcifications ; 1.9% for calcified testicular tumors , orchitis , or testicular trauma ; and 2.8% to 4.3% for scrotal calculi . the 4.3% reported by namjoshi at first sight matches perfectly with our rate of 4.8% . but namjoshi reported retrospectively on about 350 scrotal sonograms for scrotal swelling or pain , primary infertility , or past exposure to sexually transmitted diseases , whereas our series was prospective and only one case was operated on for symptomatic hydrocele . if one looks at namjoshi 's rate of 19% ( 15/78 ) for scrotal calculi in hydroceles , the detection rate for scrotal calculi by ultrasound seems to be four times that found during operation . but namjoshi 's patients all came from subtropical and tropical areas with low hygiene standards and the possibility of parasitic infection of the scrotum , whereas the possibility for such infections was very low in our patients . although calculous material within the tunica vaginalis testis is considered insignificant by most authors , sugishita et al reported on a calcified serous papillary adenocarcinoma of the tunica vaginalis . therefore , the finding of calculous or fibrous material on scrotal sonography in the tunica vaginalis testis should lead to repetition of scrotal sonography with different positioning of the patients ' body ( i.e. , supine and lateral positions ) . during sonography , calculi in hydroceles can be seen moving in the fluid between the tunica vaginalis layers ; this distinguishes them from other scrotal calcifications or pathologic findings . therefore , a differentiation between a tumor and a free calculus can be made in many cases . if the calculous or fibrous material is attached to the tunica vaginalis , however , a clear differentiation between calcification and a calcified tumour may not be possible . in symptomatic cases with doubtful or suspicious sonography , an inguinal approach to surgery should be used . for asymptomatic patients , a close follow - up including palpation and sonography infrared spectroscopy reveals the mineralogy of the scrotal calculi after operation , which in both our cases was 100% carbonate apatite . this indicates precipitation of calcium in an alkaline milieu with infection or after trauma with bleeding like in our case 1 with scarring of the tunica albuginea .
trauma , inflammation , or necrosis in the scrotal cavity may lead to depositing of organic material in hydrocele fluid with consecutive calcification if the fluid is oversaturated . during a period of 25 years 
 , 2 scrotal calculi ( calculous material in hydrocele fluid ) in 2 of 42 patients ( 4.8% ) were found during surgery on symptomatic hydroceles by the first author . in these symptomatic cases , 
 infrared spectroscopy revealed carbonate apatite as the causative mineral . 
 the appearance of scrotal calculi in hydrocele does not change the treatment or prognosis of hydroceles . however , if the calculous material is attached to the visceral or parietal part of the tunica vaginalis and does not change position during sonography with different postures , tumor growth may be a problem . 
 an inguinal approach for operation should be chosen in such situations . 
 infrared spectroscopy can be used to determine the mineralogy of scrotal calculi . 
 carbonate apatite , the predominantly found mineral in scrotal calculi , can precipitate in an alkaline milieu .