Robot-assisted radical prostatectomy (RARP) has now become a gold standard approach in radical prostatectomy. The aim of this study was to investigate incidence and risk factors of inguinal hernia (IH) after RARP.
Methods
This study included 307 consecutive men who underwent RARP for the treatment of prostate cancer from January 2011 to August 2015. The incidence of IH after RARP was investigated. Clinical and pathological factors were also investigated to assess relationship with development of postoperative IH.
Results
Median follow-ups were 380 days, and median age of patients was 67 years. Incidence of IH was 11.3, 14.0, and 15.4% at 1, 2, and 3 years after RARP, respectively. Postoperative IH occurrence was significantly associated with low surgeon experience and postoperative incontinence at 3 or 6 months after surgery (P = 0.019, P = 0.002, and P = 0.016, respectively).
Conclusions
Most of the IH occurred within the first 2 years with a rate of 14%. Incidence of IH after RARP was significantly associated with surgical experience and incontinence outcomes.
Conventional open retropubic radical prostatectomy
PSA
Prostate-specific antigen
PW
Prostate weight
RARP
Robot-assisted radical prostatectomy
RP
Radical prostatectomy
RRP
Retropubic radical prostatectomy
Background
Inguinal hernia (IH) is recognized as one of the complications of conventional open retropubic radical prostatectomy (ORRP). Regan et al. first reported IH as a complication of ORRP with an incidence of 12% at 6 months after surgery [1]. Since then, a number of studies indicated high incidence of IH after ORRP [2‐8]. In addition, various risk factors are suggested to be associated with IH after ORRP. These factors include lower body mass index (BMI), old age, and history of IH [3, 5, 9]. However, there are few studies reporting the incidence of postoperative IH after robot-assisted radical prostatectomy (RARP) [2, 10].
Our objective was to assess the incidence of postoperative IH in patients undergoing RARP and investigate relationships between clinico-pathological parameters and incidence of IH after RARP.
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Methods
Patient characteristics
This study included 307 consecutive patients who underwent RARP for prostate cancer at The University of Tokyo Hospital between January 2011 and August 2015. Surgeries were carried out by multiple surgeons using the da Vinci-S® (Intuitive Surgical Incorporation, Sunnyvale, CA) with a transperitoneal, six-port technique which was described by Menon et al. [11]. Pneumoperitoneal pressure was maintained at 10 mmHg in standard procedure, while the pressure was elevated to 15 mmHg in procedures such as resection of the dorsal vein complex and nerve preservation. The clinico-pathological demographics of patients of the present study (RARP) were collected and were analyzed in relation to postsurgical IH.
Staging was performed according to the American Joint Committee on Cancer (AJCC) TNM staging system [12]. Continence was defined as pad-free or 0 g of urinary leakage. “Low surgeon experience” was defined as surgeon experiencing less than 40 cases of RARP surgeries. Standard protocol of follow-ups after discharge was visits at 2 weeks and 1, 3, 6, 12, and every 6 months thereafter. Patients were diagnosed with IH by computed tomography for definite diagnosis.
All the patients provided a written informed consent. This study was approved by the “Ethics Committee of the University of Tokyo Hospital” (#2283) and is in accordance with the Helsinki Declaration.
Clinical characteristics of 307 patients who underwent RARP at our hospital are presented in Table 1. Median age, preoperative prostate-specific antigen (PSA) level, resected prostate weight, and body mass index were 67 years (interquartile range (IQR); 63–71), 7.7 ng/ml (IQR; 5.6–11.2), 40 grams (IQR; 30–50), and 24 kg/m2 (IQR; 22–25), respectively. Median estimated blood loss, operative, and console time were 300 ml (IQR; 150–600), 237 min (IQR; 200–274), and 183 min (IQR; 152–216), respectively.
Table 1
Characteristics of patients undergoing robot-assisted radical prostatectomy (N = 307)
Variables
Median value (IQR) or N (%)
Age (years)
67 (63–71)
Preop-PSA (ng/ml)
7.7 (5.6–11.3)
BMI (kg/m2)
24 (22–25)
History of smoking
No
118 (38%)
Yes
189 (61%)
Diabetes mellitus
Absent
263 (86%)
Present
44 (14%)
Hypertension
Absent
141 (46%)
Present
166 (54%)
Ischemic heart disease
Absent
276 (90%)
Present
31 (10%)
D’Amico risk classification
Low
51 (17%)
Intermediate-high
256 (83%)
Operative time (min)
237 (200–274)
Console time (min)
183 (152–216)
Blood loss (ml)
300 (150–600)
Nerve preservation
None
212 (69%)
Unilateral
92 (30%)
Bilateral
3 (1%)
Prostate weight (g)a
40 (30–50)
pT stage
pT2a–T2c
205 (67%)
≥pT3a
102 (33%)
Extraprostatic extension
Absent
210 (68%)
Present
97 (32%)
Resection margin
Negative
233 (76%)
Positive
74 (24%)
Preop preoperative, PSA prostate-specific antigen, BMI body mass index
aProstate weight refers to the weight of the resected prostate
A total of 30 men developed IH after RARP (Table 2). There were no significant differences in laterality. Direct hernia was observed in only one patient, and bilateral inguinal hernias were seen in 5 patients.
Table 2
Features of inguinal hernia (IH) after robot-assisted radical prostatectomy (RARP)
Incidence of IH after RARP (%)
No. of postoperative hernias
30 (100%)
Laterality
Right
13 (43%)
Left
12 (40%)
Bilateral
5 (17%)
Type
Indirect
27 (90%)
Direct
1 (3%)
Unknown
2 (7%)
Size of hernia
<1 cm
4 (13%)
1–3 cm
12 (40%)
>3 cm
7 (23%)
Unknown
7 (23%)
IH inguinal hernia, RARP robot-assisted radical prostatectomy
Kaplan-Meier curves showed proportion of IH-free rates in patients who underwent RARP (Fig. 1). Accumulative incidence of IH in patients with RARP was 11.3, 14.0, and 15.4% at 1, 2, and 3 years after surgery, respectively (Fig. 1).
Fig. 1
Kaplan-Meier curve showing proportion of inguinal hernia-free rates in patients with robot-assisted radical prostatectomy. Probability of IH-free survival after RARP is shown. IH-free rate was 88.7, 86.0, and 84.6% in the first, second, and third year
×
In the univariate analysis regarding preoperative factors, age, BMI, history of smoking, and history of IH repair were not statistically significant factors associated with incidence of IH (Table 3). In addition, preoperative comorbidities such as hypertension and diabetes mellitus were also investigated but were not significant factors (Table 3). We then investigated postoperative factors and found that low surgeon experience and incontinence at 3 or 6 months were statistically significantly associated with the incidence of IH after RARP (P = 0.019, P = 0.002, and P = 0.016, respectively (Table 4)).
Table 3
Relationships between preoperative factors (clinical factors and comorbidities) and incidence of inguinal hernia (IH) developing after robot-assisted radical prostatectomy (RARP) (N = 307)
Preoperative clinical factors
Incidence of IH after RARP
No
Yes
P value
Age (years)
<67
132 (43%)
13 (5%)
0.653
≥67
145 (47%)
17 (6%)
Body mass index (kg/m2)
<24
92 (34%)
12 (4%)
0.820
≥24
151 (55%)
18 (7%)
Smoking history
Absent
104 (34%)
14 (5%)
0.337
Present
172 (56%)
16 (5%)
History of IH repair
Absent
268 (87%)
29 (9%)
0.980
Present
9 (3%)
1 (1%)
History of lower abdominal surgery
Absent
212 (69%)
25 (8%)
0.399
Present
65 (21%)
5 (2%)
Prostate-specific antigen (ng/ml)
<8
143 (46%)
18 (6%)
0.383
≥8
134 (44%)
12 (4%)
cT stage
cT1c
225 (73%)
24 (8%)
0.870
≥cT2
52 (17%)
6 (2%)
Preoperative comorbidities
No
Yes
P value
Cerebral vascular disease
Absent
266 (87%)
28 (9%)
0.369
Present
11 (3%)
2 (1%)
Hypertension
Absent
123 (40%)
18 (6%)
0.124
Present
154 (50%)
12 (4%)
Diabetes mellitus
Absent
237 (77%)
26 (9%)
1.000
Present
40 (13%)
4 (1%)
Hyperlipidemia
Absent
198 (64%)
19 (6%)
0.399
Present
79 (26%)
11 (4%)
Ischemic heart disease
Absent
248 (81%)
28 (9%)
0.752
Present
29 (9%)
2 (2%)
Pearson’s chi-square tests were used for statistical analyses except for “diabetes mellitus”, “history of IH repair”, “cerebral vascular disease”, and “ischemic heart disease” in which Fisher’s tests were used
Table 4
Relationships between surgical and pathological factors and incidence of inguinal hernia (IH) developing after robot-assisted radical prostatectomy (RARP) (N = 307)
Surgical and pathological factors
Incidence of IH after RARP
No
Yes
P value
Surgeon experience (cases)
Low (<40)
193 (63%)
27 (9%)
0.019
High (≥40)
84 (27%)
3 (1%)
Console time (min)
<183
137 (45%)
14 (5%)
0.771
≥183
140 (46%)
16 (5%)
Nerve sparing
None
193 (63%)
19 (6%)
0.475
Performeda
84 (27%)
11 (4%)
Lymph node dissection
None
219 (71%)
25 (8%)
0.582
Performed
58 (19%)
5 (2%)
Recovery of continence after surgeryb
Absent
174 (56%)
27 (8%)
0.002
After surgery (at 3 months)c
Present
102 (33%)
3 (2%)
Recovery of continenceb
Absent
97 (39%)
19 (8%)
0.016
After surgery (at 6 months)d
Present
125 (50%)
9 (3%)
Prostate weighte (g)
<40
133 (43%)
17 (6%)
0.368
≥40
144 (47%)
13 (4%)
pT stage
≤pT2
181 (59%)
24 (8%)
0.106
≥pT3
96 (31%)
6 (2%)
Resection margin
Absent
209 (68%)
24 (8%)
0.580
Present
68 (22%)
6 (2%)
aThree were treated with bilateral nerve preservation, and the remaining 95 had unilateral nerve preservation
b“Recovery of continence” was defined as lack of necessity for using pads for urinary leakage
cN = 306
dN = 250
eProstate weight refers to the weight of the resected prostate. Pearson’s chi-square tests were used for statistical analyses
Multivariate analysis showed that low surgical experience (<40 cases) and patients who were incontinent at 3 month were significant factors associated with the occurrence of IH (P = 0.004 and P < 0.001, Table 5).
Table 5
Multivariate analysis with respect to development of inguinal hernia after robot-assisted radical prostatectomy (N = 307)
Variables
Adjusted OR (95% CI)
P value
Age (≥67 vs <67 years)
1.02 (0.46–2.30)
0.960
Smoking history (No vs ≥yes)
1.55 (0.69–3.49)
0.287
BMI (<24 vs ≥24 kg/m2)
1.06 (0.46–2.38)
0.892
History of inguinal hernia repair (yes vs no)
1.03 (0.05–6.37)
0.976
Surgical experience (<40 vs ≥40 cases)
4.74 (1.57–20.56)
0.004
Continent at 3 months (no vs ≥yes)
6.41 (2.14–27.64)
<0.001
OR odds ratio, CI confidence interval, BMI body mass index
Continence after robot-assisted radical prostatectomy was defined as pad-free (complete continence)
Logistic regression model was used for multivariate analysis
P value of <0.05 was considered to be statistically significant
Discussion
IH is regarded as one of the complications of ORRP. Incidence of IH after ORRP ranges from 12.2 to 23.9% during the first few years [2‐8]. However, incidence of IH after RARP is not well known. To our knowledge, there are only two studies regarding incidence of IH after RARP [2, 10]. A European study revealed lower incidence of IH after RARP than after ORRP (12.2 vs. 5.8% at 48 months, respectively) [2]. A study by Lee et al. reported association between the presence of patent processus vaginalis (PPV) and development of IH in patients undergoing RARP [9]. The present study shows new findings that low surgeon experience, and continence outcomes are associated with the incidence of IH after RARP.
In general, IH occurs more frequently among men with low body mass index (BMI), old age, and history of smoking [13, 14]. Anatomically, the internal orifice is penetrated by the spermatic cord and is covered by the transversalis fascia, which act as a supportive structure in preventing development of IH. Patients with overweight have excessive fat and thickness of the abdominal wall that support the preventive effect against hernia formation. Aging may abate tension of the supporting connective tissue surrounding the internal inguinal ring [15]. It may also accelerate deterioration of muscular power of the abdominal muscles [13, 16]. Smoking is a known factor that is related to an increased risk of IH recurrence, since it causes change in the collagen composition by generating tissue hypoxia [14]. However, in the present study, low BMI, aging, and smoking were not significant factors related to the incidence of IH.
Previous reports have explored to identify other factors contributing to IH after radical prostatectomy (RP), whether the surgical types to be open surgery or not. Meta-analysis showed that increasing age, low BMI, previous inguinal hernia repair, presence of postoperative anastomotic stricture, and surgical types other than laparoscopic radical prostatectomy (LRP) or radical perineal prostatectomy were the significant factors predicting occurrence of IH [17]. In the present study, none of these factors were significantly associated with incidence of IH. However, one of the novel findings of our study was that development of IH was associated with persistent incontinence at 3 or 6 months after RARP. Factors attributing to IH and failure of gaining continence may be explained from the damage to the seamless pelvic structure including the transversalis fascia and pelvic floor muscles. Excessive damage to the pelvic floor may directly influence the condition of incontinence and, at the same time, weaken tension of the transversalis fascia leading to an increased risk of postoperative IH. In addition, not well-experienced surgeon may excessively spread the working space near the internal orifice when exposing the Retzius space, which may damage the transversalis fascia. This may be the reason to why low surgeon experience was significantly associated with the incidence of IH.
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We have previously reported the incidence of IH in patients undergoing minimum incision endoscopic retropubic radical prostatectomy (MIES-RRP) and ORRP [18]. The incidence of IH after radical prostatectomy may be comparable between RARP and ORRP, since accumulative incidence of IH in patients with ORRP were 9.3% at 1 year and 13.1% at 2 years. However, it may be possible that IH may occur more frequently in patients with RARP than those with MIES-RRP, considering the fact that the accumulative incidence of IH in patients with MIES-RRP was 5.9% at 1 year and the same rate at 2 years. This is interesting since the procedures of MIES-RRP and RARP share commonality with the size of skin incision, and yet the incidence of IH seemed to be different. In MIES-RRP, surgeons have smaller limited working area due to the smaller skin incision. Whereas in RARP procedure, with its magnified vision and extended mobility, surgeons can easily achieve exposure with a wider operational area. Therefore, a smaller skin incision in MIES-RRP involves a limited exposed area attenuating the damage that may increase the risk for the development of IH. However, in RARP patients, small skin incision that is made for retrieving the prostate specimen does not affect the range and degree of exposure inside the abdomen, since this incision is made after prostatectomy. Unfortunately, a wider range of good exposure is potentially available in RARP procedure that may lead to an increased risk of developing postoperative IH. Further, based on this idea, it would be easy to understand the low incidence of IH development in patients who undergo laparoscopic radical prostatectomy [19, 20]. The limited mobility of laparoscopic instruments results in a relatively less dissection and damage to the transversalis fascia. To note, incidence of IH is surprisingly low with a range of 0–1.8% after radical perineal prostatectomy, in which the transversalis fascia is intact [21, 22].
In the future, studies demonstrating prophylactic methods may be required, since high incidence of IH is observed in RARP.
Conclusions
The present study shows that the incidence of IH in RARP patients was similar with the previous reports. Interestingly, incidence of IH after RARP was significantly associated with incontinence outcomes.
Acknowledgements
The authors would like to thank K Kawabe (former professor of Department of Urology, The University of Tokyo), T Kitamura (honorary professor of Department of Urology, The University of Tokyo), and Dr. Ishii (Ishii Clinic) for referring many patients that were included in the study.
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Funding
There were no funding to support this study.
Availability of data and materials
The datasets supporting this study are available at the Department of Urology, The University of Tokyo Hospital.
Authors’ contributions
YY collected and analyzed the data and wrote the manuscript. TF collected the data, assisted in designing the study, and also assisted on writing the manuscript. HF, TN, and HK collected the data and assisted in designing the study. TS assisted on statistical analysis. KT, SK, and MS collected the data and assisted in the statistical analysis. YI and YH assisted in the design of the study and made important suggestions in writing the manuscript. All authors read and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
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Consent for publication
Not applicable.
Ethics approval and consent to participate
This study was approved by the “Ethics Committee of the University of Tokyo Hospital” (#2283), and written informed consent was obtained from all individual patients.
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