Congenital Undescended Testis Research Articles

Evaluation and management of the infant with cryptorchidism.

Normal testicular descent is now recognized to occur in two steps with the first, transabdominal stage controlled by insulin-like hormone 3. The second, inguinoscrotal stage is controlled by androgens, mostly indirectly via the genitofemoral nerve, which appears to direct the migration of the gubernaculum to the scrotum. Undescended testis (UDT) is multifactorial, with only some of the genes identified. This review highlights recent developments that are leading to changes in practice. There is an emerging consensus among pediatric surgeons and urologists about the management of UDT with recommendations that the diagnosis of congenital UDT should be confirmed at 3-6 months of age and orchidopexy done at 6-12 months of age. With the recommendations for early surgery, recent studies focus on the complications of orchidopexy, to determine whether this is higher in infants than older children. In addition, there is general acceptance of the existence of 'acquired' UDT, which develops after about 2 years of age, but treatment for this group remains controversial. Evaluation of children with UDT now needs to be separated into the assessment of possible congenital UDT in infants at 0-6 months, for orchidopexy before 12 months, and preschool boys, who may be developing acquired UDT.

Scrotal ultrasound findings in previously congenital and acquired unilateral undescended testes and their contralateral normally descended testis.

The aim of this study was to report on different anomalies found by physical examination and scrotal ultrasound in men with previously unilateral congenital undescended testes (UDT; N=50), acquired UDT (N=49), their contralateral normally descended testis (CNDT) and control testes (N=53). Acquired UDT significantly more often had a testicular volume being <15mL than congenital UDT (88% vs. 68%). In the congenital group, significant differences were found between UDT and CNDT for soft consistency (UDT 36% vs. CNDT 14%), epididymal diameter (UDT 7.6mm vs. CNDT 8.9mm), testicular volume (UDT 9.8mL vs. CNDT 13.8mL), and inhomogeneous parenchyma (UDT 38% vs. CNDT 14%). In the acquired group, significant differences were found between UDT and CNDT for epididymal diameter (UDT 7.5mm vs. CNDT 8mm), testicular volume (UDT 9.3mL vs. CNDT 14.1mL), testicular volume <15mL (UDT 88% vs. CNDT 59%), and inhomogeneous parenchyma (UDT 27% vs. CNDT 6%). The following parameters of congenital UDT, acquired UDT, congenital CNDT, and/or acquired CNDT significantly differed compared with controls: soft testicular consistency (congenital UDT 36%, acquired UDT 20%, congenital CNDT 14%, acquired CNDT 12% vs. controls 0%), epididymal diameter (congenital UDT 7.6mm, acquired UDT 7.5mm, acquired CNDT 8mm vs. controls 9.2mm), testicular volume (congenital UDT 9.8mL, acquired UDT 9.3mL, congenital CNDT 13.8mL, acquired CNDT 14.1mL vs. control testes 15.8mL), testicular volume <15mL (congenital UDT 68%, acquired UDT 88%, congenital CNDT 66% vs. controls 43%), inhomogeneous parenchyma (congenital UDT 38%, acquired UDT 27%, congenital CNDT 14% vs. controls 0%), and testicular microlithiasis (congenital CNDT 24% vs. control testes 8%). Few differences between congenital and acquired unilateral UDT and congenital and acquired CNDT support the hypothesis of a spectrum of maldescended testes containing congenital and acquired UDT instead of them being two different entities. The CNDT also has anomalies albeit less severe than the UDT, indicating that in unilateral UDT both testes are affected.

Correlation between the androgen receptor status of the appendix testis and the efficacy of human chorionic gonadotropin treatment in undescended testis.

To compare the androgen receptor (AR) status of the appendix testis (AT) in congenital undescended and retractile testes. Twenty-four appendix testes (AT) were removed from 21 boys to detect AR expression by immunohistochemistry and immunofluorescence staining. Group 1 (n = 3) includes ATs from three patients with unilateral and group 2 (n = 6) with bilateral congenital undescended testis. All patients with bilateral form had been previously treated with human chorionic gonadotropin (hCG) without an acceptable effect. Group 3 (n = 12) includes ATs collected from 12 boys with acquired undescended testis or retractile testicle. Group 4 (n = 3) includes ATs from three young adults who received hCG treatment for undescended testis in their childhood and underwent open testicular biopsy to investigate infertility. Further seven ATs were collected to detect AR mRNA using RT-PCR analysis. Both immunohistochemistry and immunofluorescence staining of ATs showed AR expression in 100 % of the cases in groups 3 and 4 (12/12 and 3/3), but there was no visible AR expression in groups 1 and 2 (0/3 and 0/6); however, RT-PCR analysis revealed mRNA expression of AR both in congenital undescended and in retractile testicles. The presence of AR in the epithelial cells of AT in patients with retractile testicle and its absence in patients with congenital undescended testis can be a possible cause of the effectiveness of hormonal treatment in retractile testis and its inefficacy in patients with congenital undescended testis.

The independent functioning of the orchidopexied congenital undescended testis as assessed by positron emission tomography/computed tomography.

Fertility after orchidopexied undescended testes (UDT) is impaired. Although fertility parameters are known to be more favorable in unilateral cases than in bilateral cases, the exact contribution of the unilateral orchidopexied UDT to fertility is unknown. We used testicular 18F-fluoro-2-deoxyglucose (18F-FDG)-uptake assessed by positron emission tomography/computed tomography (PET/CT) to investigate the function of the orchidopexied unilateral congenital UDT, compared to its normally descended counterpart. We hypothesize that the contribution of the orchidopexied unilateral congenital UDT to fertility in adulthood is low. Eleven men who underwent orchidopexy for congenital UDT at the age of 1.9 ± 1.4 (range, 4.5 months -4.0) years were seen in follow-up at the age of 24.1 ± 2.3 (20.6-28.0) years. All underwent physical examination, testicular ultrasonography and PET/CT. Testicular 18F-FDG-uptake was expressed as the peak Standardized Uptake Value (SUVpeak). The mean SUVpeak of the orchidopexied UDT was 2.74 ± 0.48 (2.13-3.47), which was significantly lower than its counterpart (P = 0.021). Besides, there was no correlation between the testicular volume and the SUVpeak. The orchidopexied congenital UDT has been shown to be less metabolically active than its contralateral counterpart. Nevertheless, we suggest that the operated testes function to some degree.

Testicular Ascent after Laparoscopic Percutaneous Extraperitoneal Closure for Inguinal Hernias

Laparoscopic percutaneous extraperitoneal closure (LPEC) has been widely performed for the repair of pediatric inguinal hernias in Japan. This study aimed to evaluate the testicular ascent and orchiopexy after LPEC in males with inguinal hernias. The medical records of male patients who underwent LPEC procedures for the repair of an inguinal hernia from January 2010 to December 2013 at our institution were reviewed. The patients who underwent orchiopexy after the LPEC procedure were investigated, the characteristics studied were the birth weight of the patients, the age when they underwent LPEC, the mean time from LPEC to orchiopexy, and the location of the affected testes. The LPEC procedure was performed by extraperitoneal circuit suturing around the internal inguinal ring with a long straight special needle (Lapaherclosure; Hakko Medical Co., Tokyo, Japan). During the 4-year period of this study, 438 LPECs were performed on 367 male patients. Orchiopexy was performed on 14 testes (3.2%) in 10 patients who had previously undergone LPEC. Five of the 10 patients were extremely low-birth-weight infants. The mean time from LPEC to orchiopexy was 13.2 months. In 7 of these 10 patients, both testes were initially identified in the scrotum at 3 months after LPECs, but they later showed ascending or retractile testes. In another three patients, the ipsilateral testes were elevated early after LPECs, and they were thought to be missed congenital undescended testes. At orchiopexy, 10 of the 14 testes were located in the inguinal region, and the other four testes were retractile. During the orchiopexy, the remaining processus vaginalis was found to adhere to the spermatic cord in all of the patients with ascending testes. The postoperative testicular ascent should be carefully examined after the LPEC procedure in patients with pediatric inguinal hernias, especially in extremely low-birth-weight infants.

The orl rat is more responsive to methacholine challenge than wild type

BackgroundThis study presents an animal model of native airway hyperresponsiveness (AHR). AHR is a fundamental aspect of asthma and reflects an abnormal response characterized by airway narrowing following exposure to a wide variety of non-immunological stimuli. Undescended testis (UDT) is one of the most common male congenital anomalies. The orl rat is a Long Evans substrain with inherited UDT. Since boys born with congenital UDT are more likely to manifest asthma symptoms, the main aim of this study was to investigate the alternative hypothesis that orl rats have greater AHR to a methacholine aerosol challenge than wild type rats. MethodsLong Evans wild type (n = 9) and orl (n = 13) rats were anesthetized, tracheostomized, and mechanically ventilated at 4 weeks of age. Escalating concentrations of inhaled methacholine were delivered. The methacholine potency and efficacy in the strains were measured. Respiratory resistance was the primary endpoint. After the final methacholine aerosol challenge, the short-acting β2-adrenoceptor agonist albuterol was administered as an aerosol and lung/diaphragm tissues were assayed for interleukin (IL)-4, IL-6, and tumor necrosis factor (TNF)-α. Histological and histomorphometrical analyses were performed. ResultsThe methacholine concentration–response curve in the orl group indicated increased sensitivity, hyperreactivity, and exaggerated maximal response in comparison with the wild type group, indicating that orl rats had abnormally greater AHR responses to methacholine. Histological findings in orl rats showed the presence of eosinophils, unlike wild type rats. β2-Adrenoceptor agonist intervention resulted in up-regulation of IL-4 diaphragmatic levels and down-regulation of IL-4 and IL-6 in the lungs of orl rats. Conclusionorl rats had greater AHR than wild type rats during methacholine challenge, with higher IL-4 levels in diaphragmatic tissue homogenates. Positive immunostaining for IL-4 was detected in lung and diaphragmatic tissue in both strains. This model offers advantages over other pre-clinical murine models for studying potential mechanistic links between cryptorchidism and asthma. This animal model may be useful for further testing of compounds/therapeutics options for treating AHR.

Fertility potential in a cohort of 65 men with previously acquired undescended testes

PurposeTo evaluate testicular function in men with previously acquired undescended testes (AUDT) in whom spontaneous descent was awaited until puberty followed by orchiopexy in case of nondescent. MethodsAndrological evaluation including paternity, scrotal ultrasound, reproductive hormones, and semen analysis was performed in three groups: men with AUDT, healthy controls, and men with previously congenital undescended testes (CUDT). ResultsIn comparison with controls, men with AUDT more often had significantly abnormal testicular consistency, smaller testes, lower sperm concentration, and less motile sperm. Except for more often a normal testicular consistency in men with AUDT, no differences were found between men with AUDT and men with CUDT. Also, no differences were found between men with AUDT which had spontaneously descended and men who underwent orchiopexy. ConclusionsFertility potential in men with AUDT is compromised in comparison with healthy controls, but comparable with men with CUDT. This suggests that congenital and acquired UDT share the same etiology. No significant difference was found between men who had spontaneous descent and men needing orchiopexy. However, fertility potential is unknown for men after immediate surgery at diagnosis, and this should be a subject for future studies.

Management of Undescended Testis

Undescended testis (UDT) or cryptorchidism is the most common genital anomaly seen in boys and can be treated surgically by orchidopexy. The age at which orchidopexy should be performed is controversial for both congenital and acquired UDT. A decision analysis is performed in which all available knowledge is combined to assess the outcomes of orchidopexy at different ages. Without surgery, unilateral congenital UDT and bilateral congenital UDT are associated with average losses in quality-adjusted life-years (QALYs) of 1.53 QALYs (3% discounting 0.66 QALYs) and 5.23 QALYs (1.91 QALYs), respectively. Surgery reduces this QALY loss to on average 0.84 QALYs (0.21 QALYs) for unilateral UDT and 1.66 QALYs (0.40 QALYs) for bilateral UDT. Surgery at detection will lead to the lowest QALY loss of 0.91 (0.34) and 1.73 (0.60) QALYs, respectively, for unilateral and bilateral acquired UDT compared with surgery during puberty and no surgery. No sensitivity analysis is able to change the preferences for these strategies. Based on our decision analytic model using societal valuations of health outcomes, surgery for unilateral UDT (both congenital and acquired) yielded the lowest loss in QALYs. Given the modest differences in outcomes, there is room for patient (or parent) preference with respect to the performance and timing of surgery in case of unilateral UDT. For bilateral UDT (both congenital and acquired), orchidopexy at any age provides considerable benefit, in particular through improved fertility. As there is no strong effect of timing, the age at which orchidopexy is performed should be discussed with the parents and the patient. More clinical evidence on issues related to timing may in the future modify these results and hence this advice.

Orchidopexy in Late Childhood often Associated with Previously Normal Testicular Position

The aim of this study was to determine retrospectively, the prevalence of acquired undescended testis (UDT) in boys who underwent late orchidopexies, that is, performed after the age of 2 years. We included all patients who were 2 years or older when they underwent orchidopexy (ORP) for UDT at the Juliana Children's Hospital during 1996 to 2009. Previous testis position from birth until the date of ORP was obtained from youth health care records. We identified 660 boys who underwent ORP after the age of 2 years for undescended testis. For 421 of these 660 boys, the previous testicular position could be retrieved from the health records. In 143 of these 421 boys (34%), the operated testis had never been scrotal (congenital UDT), whereas in the other 278 boys (66%), a previous scrotal position had been documented twice or more (acquired UDT). Our results show that two-thirds of the boys that underwent ORP after the age of 2 had previously normal descended testes. This finding may offer an additional explanation for the discrepancy between the incidence of congenital UDT and the high rate of ORP in mid and late childhood.

Response to the Letter to the Editor on Congenital Spigelian Hernia and Undescended Testis

Response to the Letter to the Editor on Congenital Spigelian Hernia and Undescended Testis

Congenital Spigelian Hernia and Undescended Testis: Pitfalls in the Transformation of a “Coexistence” to “Sequence” and “New Syndrome”

Congenital Spigelian Hernia and Undescended Testis: Pitfalls in the Transformation of a “Coexistence” to “Sequence” and “New Syndrome”

Fertility potential in men with a history of congenital undescended testes: a long‐term follow‐up study

Men with a history of congenital undescended testes (UDT) have an increased risk of fertility problems. Despite no definitive proof, current guidelines recommend early surgical intervention because this may have a positive effect on future fertility potential by preventing degenerative changes of the testes in early life. Also surgical intervention facilitates observability of the testes in view of possible malignancy. We evaluated testicular function in adult men with previous UDT treated at different ages before puberty. A long-term follow-up study of men with previous UDT was performed. Andrological evaluation included medical history taking, physical examination, scrotal ultrasound, determination of reproductive hormones, and semen analysis. Findings were compared with those of a control group of men with normal testicular descent. The influence of age at orchiopexy on future fertility parameters was evaluated in a multivariate regression analysis. 62 men were included of whom seven had had bilateral UDT. Twenty-four patients had had their orchiopexy before the age of 24months of whom eight men had it before 12months of age. Forty-eight men had had unsuccessful luteinizing-hormone-releasing-hormone (LHRH) nasal spray treatment during childhood, whereas 14 of 24 men operated before 24months of age had not received LHRH treatment before orchiopexy. Fertility potential in men with a history of UDT is compromised in comparison with controls. We could not detect any influence of age at orchiopexy on fertility parameters. However, the number of patients operated before the age of 12months is limited. This study does not support the assumption that early orchiopexy results in better fertility potential.

Different surgical findings in congenital and acquired undescended testes

To compare surgical findings in congenital and acquired undescended testes (UDT). A review of 139 boys with 158 congenital UDT and 69 boys with 84 acquired UDT was performed. The most caudal testicular position preoperatively, testis position at surgery, patency of the processus vaginalis and epididymal anomalies were prospectively recorded. In the congenital group, orchiopexy had been performed at median age (range) 4.9 (1.5-14.6) years, while the median age (range) in the acquired group was 11.9 (3.8-23.3) years. Preoperatively, only congenital UDT were found not palpable or emergent inguinal, while only acquired UDT could be manipulated in an unstable scrotal position. In comparison with congenital UDT, acquired UDT were significantly more often located at the scrotal entrance, 27/158 vs 32/84 respectively (P < 0.001). At surgery anorchia, vanished testis or testes lying intra-abdominally were only registered in the congenital UDT group. Also 37/158 congenital UDT were located in the superficial inguinal pouch vs 52/84 of the acquired UDT (P = 0.04). In congenital UDT the processus vaginalis was wide open in 74/158, while in acquired UDT the processus vaginalis was closed in 46/84 (P < 0.001) and small open in 26/84 (P = 0.04). Epididymal anomalies were more often seen in the congenital UDT group (37%) than in the acquired group (11%). The most caudal position of congenital UDT after manipulation before surgery was at the scrotal entrance. These testes were frequently associated with epididymal anomalies and wide open processus vaginalis. This was in contrast to acquired UDT, which can often be pushed down well below the scrotal entrance and are more likely to be situated in the superficial inguinal pouch, with a normal epididymis and closed processus vaginalis.

The challenge of early surgery for cryptorchidism

In congenital cryptorchidism, a recent Nordic Consensus report recommends surgical correction at 6-12 months of age to prevent male infertility. In published series of orchiopexies the median age at surgery is often 3 years or more. The aim of this study was to evaluate whether early surgery is technically safe. The study included 356 boys with 418 orchiopexies and median 1 year of follow-up. At follow-up 367 testes were in the scrotum without iatrogenic atrophy. Eight testes were atrophied and in 43 cases a redo operation was performed to achieve a scrotal position of the testis. All acquired undescended testes had a successful result. The age at operation for the group with congenital undescended testes in the intracanalicular position or in a position close to the external inguinal annulus was 4 months to 14.5 years. In the latter group the median age at operation for the 41 failures was 2 years and 4 months, which is significantly younger than the median age for the more successful operations (3 years and 9 months). The standard orchiopexy is technically demanding in small boys. Focus on successful operative results in specialist centres is important when treating cryptorchidism with early surgery, otherwise the positive beneficial biological impact on fertility potential may be lost due to treatment failure.

Perioperative surgical findings in congenital and acquired undescended testis

Purpose Perioperative surgical findings in congenital and acquired undescended testis (UDT) were prospectively assessed. Methods We included all boys with congenital or acquired UDT who underwent orchidopexy at our hospital between January 2006 and August 2009. Perioperatively, we scored the position and volume of the testis, the insertion of the gubernaculum, the patency of the processus vaginalis, and the obtained position. Results We included 69 boys (aged 0.9-14.6 years) with 76 congenital UDT and 28 boys (aged 2.2-18.5 years) with 30 acquired UDT. In the congenital group, the testis was in intracanalicular position in 55 cases (72%), whereas in the acquired UDT group, this was in 11 cases (37%; P < .001). The insertion of the gubernaculum was at the bottom of the scrotum in 13 cases (17%) of the congenital UDT group and in 12 cases (40%) of the acquired UDT group ( P < .05). The processus vaginalis was open in 63 cases (83%) of the congenital and in 9 cases (30%) of the acquired UDT group ( P < .001). Conclusion Compared to congenital UDT, acquired UDT are more likely to be situated in the superficial inguinal pouch, to have a normal insertion of the gubernaculums, and to have a closed processus vaginalis.

Variations in Timing of Surgery Among Boys Who Underwent Orchidopexy for Cryptorchidism

Current clinical guidelines recommend that orchidopexy be performed by the age of 1 in patients with congenital undescended testis. We sought to examine trends in surgical timing and to determine what factors are associated with age at surgery. The Pediatric Health Information System (PHIS) is a national database of >40 freestanding children's hospitals. We searched the PHIS to identify boys with cryptorchidism who underwent orchidopexy between 1999 and 2008. Patient age at orchidopexy was evaluated, and we used multivariate models to determine factors associated with timing of surgery. We identified 28 204 children who underwent orchidopexy at PHIS hospitals. Of these, 14,916 (53%) were white, and 17,070 (61%) had public insurance. Only 5031 patients (18%) underwent orchidopexy by the age of 1 year; only 12,165 (43%) underwent orchidopexy by the age of 2 years. These figures remained stable over time (P=.32). After adjusting for patient clustering, race (P<.001) and insurance status (P<.001) remained associated with patient age at orchidopexy; however, the treating hospital (P<.001) was the most important factor in predicting the timing of the procedure. Only 43% had surgery by 2 years of age, which suggests that either significant numbers of boys with congenital cryptorchidism do not undergo surgery in a timely fashion or late-onset testicular ectopy is more common than generally recognized. Factors associated with the timing of orchidopexy include patient race, insurance status, and the hospital in which surgery is performed.

Testicular Microlithiasis in Boys and Young Men With Congenital or Acquired Undescended (Ascending) Testis

We assessed the prevalence of testicular microlithiasis by ultrasound in boys and young men with congenital or acquired undescended (ascending) testis. During followup for testicular growth patients with congenital or acquired undescended (ascending) testis were also screened by ultrasound for testicular microlithiasis, which was defined as echogenic foci without shadowing within the testis parenchyma. Classic microlithiasis was defined as 5 or more echogenic foci in either or both testes and limited microlithiasis as fewer than 5 foci. We performed 181 ultrasounds in 181 patients (199 congenital undescended testes) with a mean age of 12.6 years (range 2.6 to 28.6) and 636 ultrasounds in 320 patients (350 acquired undescended/ascending testes) with a mean age of 12.4 years (4.1 to 24.1). Age in both patient groups was equivalent. Median followup was 1.34 years (range 0 to 3.2). Testicular microlithiasis was found in 14 patients (2.8%), of whom 11 (2.2%) displayed classic testicular microlithiasis and 3 (0.6%) exhibited limited testicular microlithiasis. Among these 14 patients 5 had congenital undescended testes, which demonstrated classic microlithiasis. Of these 5 patients 4 had chromosomal deformities. The remaining 9 patients had acquired undescended (ascending) testis, which exhibited classic microlithiasis in 6 instances and limited microlithiasis in 3. The prevalence of testicular microlithiasis in patients with undescended testis is 2.8%. There is no difference in the prevalence of testicular microlithiasis between congenital and acquired undescended (ascending) testes.

Clinical Remarks

Surgeons who operate on patients with congenital undescended testis are often confronted with a complex picture of obvious developmental delay. In such cases, the spermatic funiculus is usually sheathed by a patent vaginal process—to the point of an “intraperitoneal” position. Testes and epididymides are occasionally dystrophic and often dissociated. We think that this explains why hormone therapy has not fulfilled the hopes that were invested in this treatment. On the other hand it is obvious that surgical treatment requires substantial surgical experience and skill because of the delicate structures. The worry is therefore whether the benefit of surgery before the first year of life is completed—which is thus far only hypothetical and not quantitatively defined—is not canceled out by a higher rate of testicular atrophy. Further developments in this respect need to be monitored closely and carefully. We cannot emphasize enough the necessity of a careful examination of the position of the testes. Too often, retractile (hypermobile) testicles are misdiagnosed as gliding testicles. The focus on congenital cryptorchidism does not take into account the not so rare patients with secondary ascended testis. Their parents are often confused by the available information—gleaned, for example, on the internet—with regard to the perceived risk of infertility and later degeneration, especially because their sons have usually exceeded the given age limit by some margin. In these cases, a differentiated and reassuring consultation should be offered, because no “primary damage” exists (guidelines). In view of the long term sequelae and the treatment delivered by doctors from different specialties and institutions, better interdisciplinary cooperation would be desirable to help answer the outstanding questions.

UPDATE ON CONGENITAL VERSUS ACQUIRED UNDESCENDED TESTES: INCIDENCE, DIAGNOSIS AND MANAGEMENT

Congenital and acquired undescended testes are two distinct entities. Current management is surgery in the first 6-12 months of life for congenital undescended testes. Current management of acquired undescended testes is surgery at the time of diagnosis. Accurate diagnoses and expedient management are imperative in this condition to minimize the long-term sequelae of infertility and testicular cancer.

Differential expression of androgen and estrogen receptor of appendix testis in patients with descended and undescended testes

The incidence of appendix testis has been shown to be 76% in descended and 24% in undescended testis in our previous intraoperative survey. To determine the possible role of the appendix testis in the process of testicular migration, we compared the androgen and estrogen receptor status of appendix testis in descended and undescended testes. Thirty-seven appendix testes were collected intraoperatively and the expression of androgen and estrogen receptors were examined with immunostaining and immunofluorescence labeling. Based on the diagnosis, the specimens were divided into three groups. Group H (groin hernia, n = 11, as a group of descended testis), Group AU (acquired undescended testis, n = 14), and Group CU (congenital undescended testis, n = 12). The testicular appendages were found to express both androgen and estrogen receptors in Group H and Group AU, but specimens in Group CU were only estrogen receptor positive, whereas androgen receptors were not present. The presence of the androgen receptor in the appendix testis of the descended testes and acquired undescended testes and its absence in patients with congenital undescended testis suggests that the appendix testis might play a role in the process of testicular descent.