Kaname Ameda
Harvard University
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Featured researches published by Kaname Ameda.
The Journal of Urology | 1999
Kaname Ameda; Maryrose P. Sullivan; Robert J. Bae; Subbarao V. Yalla
PURPOSE The pathogenesis of lower urinary tract symptoms in men without bladder outlet obstruction has not been well characterized. Therefore, we defined the urodynamic abnormalities associated with symptomatic nonobstructive voiding dysfunction, and determined the relationship between age and type of dysfunction. MATERIALS AND METHODS Video urodynamic studies of symptomatic men without outlet obstruction were examined. The criterion for a normal bladder outlet was a pressure gradient across the prostatic urethra of 5 cm. water or less in the absence of distal stricture. A maximum isometric contraction pressure less than 60 cm. water was regarded as impaired detrusor contractility. Detrusor instability was defined as involuntary detrusor contractions during filling or the inability to suppress a detrusor contraction after initiation of flow. Patients were categorized into 4 groups based on the urodynamic findings. RESULTS Of 193 men (mean age 69.6+/-10.5 years) 40.9% had detrusor instability (group 1), 31.1% had impaired contractility (group 2), 10.8% had detrusor instability and impaired contractility (group 3), and 17.1% were urodynamically normal (group 4). Average patient age was significantly lower in group 4 than all other groups. Bladder capacity was lowest in group 1, and group 3 had the lowest voiding efficiency. Maximum flow rate, bladder compliance and symptom scores were not different among the 4 groups. The prevalence of detrusor instability with and without impaired contractility increased, while the proportion of patients without urodynamic abnormalities decreased with age. Bladder contractility did not correlate with age. CONCLUSIONS The nonobstructed patient population comprises several groups that are functionally distinct while symptomatically similar. Thus, treatment of nonobstructed cases based on symptoms may lead to inappropriate pharmacological therapy and unsuccessful clinical outcomes.
The Journal of Urology | 1998
Kaname Ameda; Graeme S. Steele; Maryrose P. Sullivan; Doron Stember; Subbarao V. Yalla
PURPOSE Recent studies suggest that detrusor contraction duration increases with bladder outlet obstruction and correlates with the American Urological Association (AUA) symptom index. Since the detrusor contraction duration may also depend on detrusor contractility and bladder volume, its use alone in characterizing bladder outlet obstruction is debatable. Therefore, we studied the relationship between detrusor contraction duration and bladder outlet obstruction, bladder capacity, detrusor contractility and symptoms to determine whether detrusor contraction duration is a useful parameter for characterizing bladder outlet obstruction in men with lower urinary tract symptoms. MATERIALS AND METHODS Pressure-flow studies were performed in men with lower urinary tract symptoms. Bladder outlet obstruction was defined as passive urethral resistance relation greater than grade II and contractility was determined from Schäfers nomogram. Detrusor contraction duration was defined as the contraction time elapsed between the first rise in detrusor pressure from baseline to the time at which detrusor pressure returned to baseline at the end of voiding. AUA symptom index was attained from each patient and categorized as mild (0 to 7), moderate (8 to 19) and severe (20 to 35). RESULTS Detrusor contraction duration was determined from 58 consecutive pressure-flow studies. This parameter was not significantly different among 23 patients with mild (116.7+/-34.0 seconds), 15 with moderate (102.7+/-61.9 seconds) and 9 with severe (89.2+/-44.4 seconds) AUA symptom index scores. AUA symptom index, as well as irritative and obstructive scores did not significantly correlate with detrusor contraction duration. Detrusor pressure at maximal flow was weakly correlated with detrusor contraction duration (r=0.322, p=0.014). However, detrusor contraction duration in 27 obstructed patients (111.6+/-53.7 seconds) was not significantly different from that of 31 nonobstructed patients (91.5+/-41.5 seconds) and it did not increase with the severity of bladder outlet obstruction. Detrusor contraction duration in 40 patients with good contractility (94.3+/-49.2 seconds) was significantly lower than in 18 patients with poor contractility (115.5+/-43.3 seconds). Detrusor contraction duration was significantly lower in nonobstructed patients with good contractility (72.0+/-21.7 seconds) compared with either nonobstructed patients with poor contractility (118.4+/-47.7 seconds) or obstructed patients with good contractility (112.5+/-58.0 seconds). There was no difference in detrusor contraction duration between nonobstructed patients with poor contractility and obstructed patients with good contractility. Multiple regression analysis showed that detrusor contraction duration can be best predicted by a combination of detrusor pressure at maximal flow, bladder capacity and contractility (r=0.576). CONCLUSIONS Our study showed that detrusor contraction duration cannot distinguish patients with from those without bladder outlet obstruction, and it does not correlate with the severity of symptoms. Since our results also showed that detrusor contraction duration depends on several factors related to detrusor and outlet function, it cannot be used as a reliable parameter to diagnose bladder outlet obstruction.
Diagnostic and Therapeutic Endoscopy | 1997
Toshiki Koyama; Katsuya Nonomura; Kaname Ameda; Hidehiro Kakizaki; Yasukuni Matsugase; Yuichiro Shinno; Takayuki Kanno; Tetsufumi Yamashita; Masashi Murakumo; Tomohiko Koyanagi
From June 1992 to December 1996, we performed laparoscopic evaluation for 28 nonpalpable testes in 22 patients (1–21, median 3 years old). The location of 28 testes were divided into 4 categories according to the classification by Malone et al.: canalicular in 17 testes, just canalicular in 2, abdominal in 7, and absent in 2. Two-stage Fowler–Stephens orchiopexy was performed in 3 abdominal testes and planned two-stage orchiopexy was performed in one abdominal testis, while one-stage standard orchiopexy was performed in 10 testes (canalicular 5, just canalicular 2, and abdominal 3). In 10 of 17 canalicular testes no testicular element was found on histological examination of the excised remnant tissue. In two completely absent testicular structures, as verified by vanishing spermatic vessels, no further exploration was done after laparoscopy. There was one complication in this series: jejunal injury which needed oversewing, otherwise there was no postoperative sequela in all cases. Laparoscopic evaluation in patients with nonpalpable testes gives us precise information as to the existence and location of the testicle which is helpful in determining subsequent appropriate procedure and avoiding unnecessary abdominal exploration.
Diagnostic and Therapeutic Endoscopy | 1998
Ken Morita; Katsuya Nonomura; Kaname Ameda; Hidehiro Kakizaki; Toshiki Koyama; Tetsufumi Yamashita; Masashi Murakumo; Tomohiko Koyanagi
The use of laparoscopic technique to diagnose and treat intersex children is gradually introduced in clinical urology. From 1985 to 1996, abdominal exploration and gonadectomy were performed in 11 intersex children together with urogenital endoscopy and genitoplastic surgery in our institutes. Their median age was 6.0 (range 0–15) years old and initial gender sex was female in 8 and male in 3. The initial 4 cases (group 1) underwent open abdominal exploration together with gonadectomy, while the latter 7 cases (group 2) underwent laparoscopic exploration simultaneously with 3 laparoscopic gonadectomy and 1 open one via a inguinal incision. Their final diagnoses were male pseudohermaphroditism in 4 cases, mixed gonadal dysgenesis in 3, true hermaphroditism in 2, XX gonadal dysgenesis in 1, and XY gonadal dysgenesis in 1. Consequently, 2 of initial male were reared as a female. Operation time, use of analgesics, postoperative hospital stay and postoperative complications were not significantly different between the two groups, however, postoperative abdominal wound appearance was more acceptable in group 2. The most significant advantage of laparoscopic surgery in intersex children is cosmetic appearance especially when social gender is determined as female irrespective types of intersexuality.
Journal of Neurophysiology | 2001
Takahiko Mitsui; Hidehiro Kakizaki; Shinobu Matsuura; Kaname Ameda; Mitsuhiro Yoshioka; Tomohiko Koyanagi
American Journal of Physiology-regulatory Integrative and Comparative Physiology | 2002
Takahiko Mitsui; Hidehiro Kakizaki; Shinobu Matsuura; Hiroshi Tanaka; Kaname Ameda; Mitsuhiro Yoshioka; Tomohiko Koyanagi
The Japanese Journal of Urology | 1997
Takashige Abe; Kaname Ameda; Tetsufumi Yamashita; Takashi Shibata; Toshimori Seki; Katsuya Nonomura; Tomohiko Koyanagi; Masayoshi Miura; Kenichi Toyoda; Nobumichi Abe; Hiromichi Kijima
The Journal of Urology | 1987
Tomohiko Koyanagi; Katsuya Nonomura; Kaori Imanaka; Toshiaki Gotoh; Kaname Ameda
ics.org | 2013
Naoki Wada; Kaname Ameda; Hiroki Okada; Ichiro Date; Kazumi Hashizume; Masafumi Kita; Tatsuya Iwata; Seiji Matsumoto; Hidehiro Kakizaki
Archive | 2001
Takahiko Mitsui; Hidehiro Kakizaki; Shuji Matsuura; Kaname Ameda; Miyako Yoshioka; Takeshi Koyanagi