Phase 2 – Interviewing process

49 CHAPTERSIX

50 true, it could explain why his mean actual testicular volume is lower since testicular volume (though relatively constant after puberty) has been found to start decreasing from the eight decade of life.^42,43 However in this study, there was no clear relationship between testicular volume and advancing age unlike the study by Handelsman et al⁴² . Also the fact that we studied different population group; they studied people in Tokyo Japan and I studied the population in Nnewi Nigeria could account for the difference. Since environment and race have also been found to influence testis volume.^27,46,48

ACCURACY OF PRADER ORCHIDOMETER

The Prader orchidometer overestimated testicular volume by 25.14%

(2.66mls) in this study. It has been shown to overestimate the actual testicular volume by a lot of other studies to varying degrees.^25,28,66 Paltiel et al²⁷ in their study of 18 canine testes showed the orchidometer overestimated testicular volume by only 12%(1.6ml). The actual cause of this difference is not certain but it should be noted that he used dog testes and not human testes. Secondly, he did not measure the actual size of testes by water displacement like was done in this study. He got the testicular volume by weighing the testis and converting with the formula volume= weight/density while assuming that the density of dog testis is the same for human testis.

Though the density of human testis has been found to be constant at 1.038 by Handerlsman et al⁴² the assumption by Paltiel et al²⁷ that the density of dog testes should be the same as that of humans is not entirely correct. In addition, the skin of dog scrotum may also have a different texture compared to that of human scrotum.

51 On the other hand, Sakamoto et al²⁸ found that Prader orchidometer overestimated the mean testicular volume by 81.7% (6.68ml). In his methodology, though they said the Prader orchidometer measurement was done by one experienced urologist, no mention was made of whether he attempted to exclude the epididymis which is one of the things that have been found to reduce the accuracy of Prader orchidometer.^9,31,36 Also it was not mentioned if the water displacement was done by the same urologist or if he was aware of the ultrasound results. These factors have been suggested as likely to improve the accuracy of the orchidometer measurement.⁶⁴

Rivkees et al²⁵ showed that Prader orchidometer only over estimated by 30%. In his study however, he used animal models. They used the testes of 10 calves and 9 dogs and an artificial scrotum to simulate human scrotum.

They also found that Prader orchidometer overestimates testicular volume to varying degrees depending on the size but no mention was made of the average volume of the testes they measured. The smaller the testis the more the overestimation and vice versa, thus mention of the mean size of the testes measured would have been most appropriate.5,25,26,31,63

In this study it was found that Prader orchidometer volume measurements correlated strongly with the actual testicular volumes measured by water displacement using Pearson correlation coefficient (r=0.921,P=0.0001). There is no consensus by previous studies on whether or not Prader orchidometer measurements correlate with actual testicular volume measurements. While some say it correlates strongly, others say it does not.^27,28,66 Sakamoto et al²⁸ found a strong correlation between the two (r=0.818, p=0.0001) though lower than what was got in this study. Paltiel et

52 al²⁷ on the other hand did not find a statistically significant correlation between Prader orchidometer and actual testicular volumes (r²=0.14, p=0.12).

Though they worked on animals and did not use the actual volume but a derived one like the one highlighted above, all these go to show the variability in the results produced by Prader orchidometer.

ACCURACY OF ULTRASOUND

All the ultrasound formulas in this study underestimated the actual testicular volume. Formula 1 (LWHx0.52) underestimated the actual testicular volume by 2.97ml (28.04%), formula 2 (LW²x0.52) by 4.08ml(38.54%) and formula 3 (LWHx0.71) by 0.41(3.89%). This means that formula 3 was the most accurate of the three ultrasound formulas in this study.

Sakamoto et al²⁸ in their work found that ultrasound formula 1 underestimated by 1.9ml (21.3%), formula 2 underestimated by 3.35ml (37.6%) and formula 3 overestimated by 0.8ml(7.46%). Though slightly different from this study, they also noted the most accurate formula to be formula 3. The slight difference in level of underestimation by ultrasound scan in these two studies could be accounted for by the difference in the actual testicular volume measured by water displacement (10.59ml in this study and 9.27ml by Sakamoto et al²⁸). In addition, noticing that the result of the three formulas from the two studies vary by a range of 0.39ml to 1.07ml (1.07ml for formula 1, 0.73ml for formula 2 and 0.39 for formula 3) all within the confines of the mean difference in actual testicular volume between the two studies may mean the difference is only minimal.

53 Another reason could be the difference in sample size. They studied 40 testes while I studied 121testes.

Hsieh et al⁶⁶ got 3.3ml ( 31.4%), 1.8ml (17.2%) and 0.6ml (6.3%) for formula 1, formula 2 and formula 3 respectively. Their mean actual testicular volume is the same with that of this study (10.6ml).The difference being 0.33mls for formula 1, 2.28ml for formula 2 and 0.2ml for formula 3. Except for formula 2, the difference in the two studies is less than 0.5ml, that is approximately 3%. This could be from the operator factor of the ultrasound.

Paltiel et al²⁷ in their work on canine testes also noted that the most accurate of the ultrasound formulas was formula 3. In their work, formula1 underestimated by 1.9ml (31%) and formula 2 by 1.1ml (11%) and they noted that formula 3 caused the least mean bias but did not give the value.

Rivkees et al²⁵ in their earlier work in1987 when the best formula was not an issue, used only formula 2 on 10 calves and 9 dogs with a simulated scrotum. They found that this formula had an accuracy of 4.6% + 1.6%. This is however not consistent with any of the studies mentioned earlier. This may be because they worked on scrotum that was simulated by double sheep skin.

In this study, it was also found that the ultrasound results correlated strongly with the actual testicular volume, which is in keeping with what other workers had reported.

Thus, all the previous works where all the three formulas were used were unanimous in the superiority of formula 3 and the strong correlation of all ultrasound formulas with the actual testicular volume.

54 RELATIONSHIP BETWEEN ULTRASOUND AND PRADER

ORCHIDOMETER.

Orchidometer in this study always overestimated the testicular volume measured by ultrasound, which is similar to what some studies had reported.27-31,63-65. It also has a strong correlation with all the three ultrasound formulas. Schiff et al²⁴ however think orchidometer is as accurate as ultrasound when the orchidometer is used by an experienced practitioner. In their study, though the mean testicular volume by ultrasound and Prader orchidometer were the same, the correlation coefficient of r²= 0.52 and 0.48 for right and left testis respectively is low compared to other study.^27,28,66. This means there is no consistency in the estimation by orchidometer for individual testis. Some overestimated while some underestimated so cancelling out to give equal mean testicular volumes. The paired t test significance is also very high (p= 0.49 and 0.81 for right and left testes respectively) as against this study where p= 0.0001.

As counseled by Tatsunami et al,⁶⁴ proper standardization of the Prader orchidometer measurement technique such as periodic comparison with ultrasonography results will be necessary to improve accuracy^.

Suffice it to say that an instrument like the Prader orchidometer which gives a range of overestimation of between 15% and 87.1% in just four studies leaves much to be desired. This makes it difficult to recommend its use for measuring testes when minute details are expected as is required occasionally for evaluation of varicoceles.

55 CHAPTER SEVEN