Contralateral Metachronous Hernia Following Negative Laparoscopic Evaluation for Contralateral Patent Processus Vaginalis: A Meta-analysis

Abstract

Objective:

To conduct a meta-analysis of contralateral metachronous inguinal hernia (CMIH) that originated from negative laparoscopic evaluation for contralateral patent processus vaginalis (CPPV) in children who presented with a unilateral inguinal hernia and to determine the incidence of and factors associated with such a CMIH.

Materials and Methods:

A PubMed search was performed for all studies concerning laparoscopic repair or evaluation of inguinal hernia in children. The search strategy was as follows: (laparoscop* OR coelioscop* OR peritoneoscop* OR laparoendoscop* OR minilaparoscop*) AND (“inguinal hernia” OR “metachronous hernia”) AND child*. Inclusion criteria included unilateral inguinal hernia in children, negative laparoscopic evaluation of CPPV, without history of contralateral inguinal surgery previously, and clearly reporting CMIH development or not. Editorials, letters, review articles, case reports, animal studies, and duplicate patient series were excluded.

Results:

Twenty-three studies comprising 6091 children with negative CPPV fulfilled the inclusion criteria and were included in the final analysis, of whom 80 (1.31%) subsequently presented with a CMIH. Subgroup analysis showed that CMIH incidence was lower through an umbilical approach than via an inguinal one (0.85% versus 1.78%, P=.009). As for the transinguinal approach, there was a CMIH incidence of 0.78% and 2.05%, respectively, for laparoscopy with a small angle (30° and 70°), whereas there was no CMIH development for that with a large angle (110°, 120°, and flexible). A high pneumoperitoneum pressure (>10 mm Hg, >12 mm Hg, and >14 mm Hg) was usually associated with a slightly higher CMIH incidence than a low one (≤10 mm Hg, ≤12 mm Hg, and ≤14 mm Hg), all without significant difference. CMIH incidence was slightly lower for using a broad CPPV definition than for using a narrow one (0.64% versus 1.35%, P=.183).

Conclusions:

CMIH following negative laparoscopic evaluation for CPPV was a rare but possible phenomenon. Choosing the transumbilical approach, transinguinal laparoscopy with a large angle, low-pressure pneumoperitoneum, and broad CPPV definition would probably reduce the occurrence of such CMIHs.

Introduction

Contralateral metachronous inguinal hernia (CMIH) was frequent after repair of a unilateral inguinal hernia in children. Although the mechanism of CMIH is still unclear, currently most authors are in harmony that all CMIHs are preceded by a contralateral patent processus vaginalis (CPPV). In order to avoid CMIH development and its potential risk of incarceration, some authors advocated open contralateral exploration and ligation of CPPV if present. However, the postoperative risks, including testicular atrophy, vas deferens injury, and even infertility, could not be neglected.^1–3

Laparoscopy had been widely used to evaluate CPPV without injury to the vas and vessels and proved to be both sensitive (99.4%) and specific (99.5%).⁴ In recent years, there have been a large number of studies regarding laparoscopic evaluation of CPPV and CMIH development. However, studies on CMIH following negative laparoscopic evaluation for CPPV are rare.

In this study, we performed a meta-analysis of the CMIH that originated from negative laparoscopic evaluation for CPPV in children who presented with a unilateral inguinal hernia. Our aim was to determine the incidence of and factors associated with such CMIH.

Materials and Methods

A search was carried out for all studies concerning laparoscopic repair or evaluation of inguinal hernia in children, which were published in PubMed. The search strategy was as follows: (laparoscop* OR coelioscop* OR peritoneoscop* OR laparoendoscop* OR minilaparoscop*) AND (“inguinal hernia” OR “metachronous hernia”) AND child*. No lower date or language limits were set. All titles and/or abstracts were reviewed initially to select studies if they contained results of laparoscopic evaluation of CPPV in children. After identification of the titles and/or abstracts, the full text of all potentially relevant studies was retrieved. The reference lists of included studies were examined manually to identify any additional relevant studies. When the results of a single study were reported in more than one publication, only the most recent and complete data were included in the meta-analysis. The last search was performed on March 13, 2013.

For inclusion in the meta-analysis, the studies had to fulfill the following criteria: unilateral inguinal hernia in children, negative laparoscopic evaluation of CPPV, without history of contralateral inguinal surgery previously, and clearly reporting CMIH development or not. Editorials, letters, review articles, case reports, animal studies, and duplicate patient series were excluded.

Data were extracted from each study using a predefined extraction form. The extracted data included first author, year of publication, level of evidence, surgical details, definition of CPPV, demographics of patients with negative CPPV and positive CMIH (e.g., age, number, gender, and laterality), time to occurrence of CMIH, and length of follow-up. Level of evidence was classified according to the Oxford Center for Evidence-Based Medicine.⁵ Surgical details included approach of laparoscopic exploration, visible angle of laparoscopy, and pneumoperitoneum pressure.

The outcome measure was the incidence of CMIH, which was calculated according to the number of negative CPPV and the subsequent positive CMIH. Given that the direction and magnitude of CMIH incidence among studies may differ depending on many factors (e.g., experience of surgeon, method of laparoscopic exploration, development of abdominal wall, direction of inguinal canal, and individual differences), subgroup analysis was performed across a variety of related study characteristics as much as possible.

The chi-squared or Fisher's exact test was used to evaluate the significance of differences between subgroups. All tests were two sided, and P<.05 was considered statistically significant. All analyses were performed using the SPSS version 17.0 software package (SPSS, Inc., Chicago, IL).

Results

From the 329 citations initially identified, 23 studies^6–28 fulfilled the predefined inclusion criteria and were included in the final analysis (Fig. 1). The included studies comprised 6091 children with negative CPPV, of whom 80 (1.31%) subsequently presented with a CMIH in the follow-up.

FIG. 1.

Flowchart of the search process.

Characteristics of studies and patients

The characteristics of included studies are summarized in Table 1. Of the 23 included studies, 20^{6–11,13,15,16,18–28} were case series (Level 4), and three^12,14,17 were cohort studies (Level 3). Patients' ages ranged from 1 day to 19 years. The laparoscopic exploration was performed through an umbilical approach in 6 studies,^{6,8,11,13,20,27} an inguinal approach in 13 studies,^{7,9,10,15,17–19,21–24,26,28} and a combined approach in 4 studies.^12,14,16,25 The visible angle of laparoscopy included 30°, 70°, 110°, 120°, and flexible. Pneumoperitoneum pressure was between 6 and 15 mm Hg in 13 studies,^{8–11,15–17,19–21,23,25,27} whereas it was unknown in the other 10 studies.^{6,7,12–14,18,22,24,26,28} The definition of CPPV included (1) an open tunnel into the contralateral inguinal region, (2) swelling or palpable crepitus under pneumoperitoneum pressure in the contralateral groin or scrotum, and (3) bubbles or fluid expressed by palpation over the contralateral inguinal canal or scrotum. The number of negative CPPV and the subsequent positive CMIH was between 3 to 1291 and 0 to 32, respectively. The incidence of CMIH was between 0% and 5.3%. Follow-up ranged from 1 week to 14 years.

Table 1.

Characteristics of Included Studies

Reference (year)	Level of evidence	Age (years)	Approach of exploration	Visible angle of laparoscopy	Pressure of pneumoperitoneum (mm Hg)	Definition of CPPV ^a	Number of negative CPPV	Number of CMIH (incidence)	Length of follow-up (years)
Tam et al.⁶ (2013)	4	0.08–15	Transumbilical	NA	NA	(1)	293	9 (3.1%)	0.42–0.67
Juang et al.⁷ (2012)	4	NA	Transinguinal	70°	NA	(1)	1291	32 (2.5%)	1–9
Boo et al.⁸ (2012)	4	0.02–15	Transumbilical	30°	8–12	NA	115	0	0.33–2.83
Draus et al.⁹ (2011)	4	1.1	Transinguinal	70°	8	NA	441	6 (1.6%)	2–7
Saad et al.¹⁰ (2011)	4	0.02–18	Transinguinal	30°	8–15	(1)	764	6 (0.79%)	1–10
Tsai et al.¹¹ (2011)	4	0.08–16	Transumbilical	30°	8–10	NA	79	0	1–5
Niyogi et al.¹² (2010)	3	<1	Transinguinal	70°	NA	(1) (2)	67	2 (2.99%)	0.12–1
Niyogi et al.¹² (2010)	3	<1	Transumbilical	30°	NA	(1)	42	0	0.12–1
Parelkar et al.¹³ (2010)	4	0.08–11	Transumbilical	NA	NA	NA	348	0	0.02–9
Endo et al.¹⁴ (2009)	3	3.7±3.2	Transinguinal	70°	NA	NA	189	3 (1.59%)	1–11
Endo et al.¹⁴ (2009)	3	3.8±2.9	Transumbilical	70°	NA	NA	636	5 (0.79%)	1–11
Maddox and Smith¹⁵ (2008)	4	0.00319	Transinguinal	70° or 110°	15	(1) (2)	131	7 (5.3%)	≥1.58
Valusek et al.¹⁶ (2006)	4	<10	Transumbilical or transinguinal	70°	10	(1)	706	5 (0.7%)	3–14
Tamaddon et al.¹⁷ (2005)	3	0.08–10	Transinguinal	120°	10	(1) (2) (3)	49	0	3.75–4.83
Geisler et al.¹⁸ (2001)	4	0.003–13	Transinguinal	70°	NA	NA	181	3 (1.7%)	3–5
Liu et al.¹⁹ (2000)	4	NA	Transinguinal	70°	10	(1) (3)	120	1 (0.83%)	5
Owings and Georgeson²⁰ (2000)	4	<1	Transumbilical	NA	15	(1)	102	0	0.25–4.75
Gardner et al.²¹ (1998)	4	0.8–14	Transinguinal	Flexible	8–10	(1)	20	0	1.5–2.67
Pavlovich et al.²² (1998)	4	0.33–12	Transinguinal	Flexible or 70°	NA	NA	29	0	2.17
Wulkan et al.²³ (1996)	4	0.33–12	Transinguinal	30° or 70°	6–8	(1) (3)	43	1 (2.33%)	1–2.42
Fuenfer et al.²⁴ (1996)	4	NA	Transinguinal	110°	NA	(1)	87	0	2
Holcomb et al.²⁵ (1996)	4	<10	Transumbilical or transinguinal	30° or 70°	15	(1) (2)	304	0	0.17–3.42
Kaufman et al.²⁶ (1996)	4	0.12–4	Transinguinal	110°	NA	(1) (3)	11	0	0.5–1.5
Grossmann et al.²⁷ (1995)	4	3.31–3.35	Transumbilical	30°	8–14	(1) (3)	30	0	≥1
Hatch and Trockman²⁸ (1994)	4	NA	Transinguinal	30°	NA	N/A	3	0	1.42

Defined as (1) an open tunnel into the contralateral inguinal region, (2) inguinal or scrotal swelling or palpable crepitus during the laparoscopic exploration, and/or (3) bubbles or fluid expressed by palpation over the inguinal canal or scrotum.

CMIH, contralateral metachronous inguinal hernia; CPPV, contralateral patent processus vaginalis; NA, not available.

The characteristics of negative CPPV and/or the following positive CMIH were rarely documented, as shown in Table 2. Among the 23 studies, only 1 study⁶ reported the laterality of nine CMIHs (right, n=5; left, n=4), 4 studies^6,7,10,19 reported the gender (male, n=47; female, n=1) and age of initial surgery (2 weeks–13 years) of 48 children with CMIH, 5 studies^6,7,10,18,23 reported the time to occurrence of 51 CMIHs (4–42 months), and 6 studies^{6,13,21,23,25,26} reported the laterality or gender of patients with negative CPPV.

Table 2.

Characteristics of Negative Contralateral Patent Processus Vaginalis and Positive Contralateral Metachronous Inguinal Hernia

	Negative CPPV			CMIH
Reference (year)	Total	R/L	M/F	Total	R/L	M/F	Age (years) at initial surgery	Time (months) to occurrence of CMIH
Tam et al.⁶ (2013)	293	177/116	246/47	9	5/4	9/0	0.08–7	6–42
Juang et al.⁷ (2012)	1291	NA	NA	32	NA	32/0	3.56	16.7
Saad et al.¹⁰ (2011)	764	NA	NA	6	NA	5/1	0.04, 4, 5, 8, 10, 13	0.93, 3, 6, 24, 36, 36
Parelkar et al.¹³ (2010)	348	NA	282/66	0	NA	NA	NA	—
Geisler et al.¹⁸ (2001)	181	NA	NA	3	NA	NA	NA	4, 8, 9
Liu et al.¹⁹ (2000)	120	NA	NA	1	NA	1/0	<2	NA
Gardner et al.²¹ (1998)	20	14/6	NA	0	NA	NA	NA	—
Wulkan et al.²³ (1996)	43	NA	34/9	1	NA	NA	NA	12
Holcomb et al.²⁵ (1996)	304	NA	276/27	0	NA	NA	NA	—
Kaufman et al.²⁶ (1996)	11	4/7	NA	0	NA	NA	NA	—

CPPV, contralateral patent processus vaginalis; CMIH, contralateral metachronous inguinal hernia; F, female; L, left; M, male; NA, not available; R, right.

Subgroup analysis

Subgroup analysis showed that the incidence of CMIH was lower through an umbilical approach than via an inguinal approach (0.85% versus 1.78%), and the difference between the two approaches was statistically significant (P=.009), as shown in Table 3.

Table 3.

Subgroup Analysis

Group	Incidence of CMIH	P value
Approach of exploration		.009
Transumbilical	14/1631 (0.85%)
Transinguinal	61/3365 (1.78%)
Pressure of pneumoperitoneum
≤8 mm Hg	7/484 (1.45%)	.068
>8 mm Hg	13/1413 (0.92%)
≤10 mm Hg	13/1458 (0.89%)	.448
>10 mm Hg	7/537 (1.3%)
≤12 mm Hg	13/1688 (0.83%)	.292
>12 mm Hg	7/537 (1.3%)
≤14 mm Hg	13/1633 (0.81%)	.300
>14 mm Hg	7/537 (1.3%)
Definition of CPPV
Narrow definition^a	69/5036 (1.35%)	.183
Broad definition^b	4/620 (0.64%)

The narrow definition of contralateral patent processus vaginalis (CPPV) was an open tunnel into the contralateral inguinal region or no clear description.

The broad definition included at least two of the following items: (1) an open tunnel into the contralateral inguinal region; (2) swelling or palpable crepitus under pneumoperitoneum pressure in the contralateral groin or scrotum; and/or (3) bubbles or fluid expressed by palpation over the contralateral inguinal canal or scrotum.

CMIH, contralateral metachronous inguinal hernia.

As for the transinguinal approach, there was a CMIH incidence of 0.78% (6/767) and 2.05% (47/2290), respectively, for laparoscopy with a small angle (30° and 70°), whereas there was no CMIH development for that with a large angle (110°, 120°, and flexible).

A high pneumoperitoneum pressure (>10 mm Hg, >12 mm Hg, and >14 mm Hg) was usually associated with a slightly higher CMIH incidence than a low one, all without significant difference. However, it was not always the case as the CMIH incidence was lower for pressure >8 mm Hg than for pressure ≤8 mm Hg (0.92% versus 1.45%, P=.068), as shown in Table 3.

For the ease of being compared and analyzed, the definition of CPPV was divided into a narrow one and a broad one. The narrow definition of CPPV was an open tunnel into the contralateral inguinal region or no clear description, whereas the broad definition included at least two items of the CPPV definition given previously. Subgroup analysis demonstrated that the incidence of CMIH was slightly lower for using a broad definition than for using a narrow one (0.64% versus 1.35%, P=.183), as shown in Table 3.

Discussion

The false-negative incidence of laparoscopic CPPV evaluation was low.⁴ Also, not every CPPV would develop into clinically apparent hernia.²⁹ Therefore, the occurrence of CMIH deriving from a false-negative CPPV was extremely rare.^6,7 Nevertheless, we could not neglect this real but uncommon phenomenon. Meta-analysis showed that approximately 1.32% (80/6081) of negative CPPVs would proceed with a CMIH during a follow-up spanning 1 week to 11 years. Although the pooled CMIH incidence was not high, there were significant variations of incidence among included studies. Therefore, it was necessary to explore the factors associated with such CMIHs.

Subgroup analysis indicated that the CMIH incidence was lower for the transumbilical approach than the transinguinal approach, whereas for the transinguinal approach, there was no CMIH development using laparoscopy with a large angle. Our result was consistent with other authors. Niyogi et al.¹² and Endo et al.¹⁴ found that the transumbilical approach had a higher rate of CPPV detection and a lower incidence of CMIH than the transinguinal approach. Tamaddon et al.¹⁷ performed transinguinal laparoscopic evaluation of CPPV for the same 81 children with unilateral inguinal hernia using both 70° and 120° endoscopy; they found that CPPV was detected in 31 patients (38%) with the 120° endoscope and in only 23 patients (28%) with the 70° endoscope, and the 120° endoscope provided superior visualization and identification of CPPV. It might be because of obscuration of the medial umbilical fold and the natural direction of the inguinal canal, laparoscopic evaluation through the umbilicus had undoubtedly improved visibility and identification of a CPPV; in terms of the transinguinal approach, it was easier for laparoscopy with a large angle to overcome the difficulties brought by these natural factors.

Juang et al.⁷ thought that insufflation under pressure created a parachute effect or overdistention of the CPPV, which would appear to obliterate the potential tunnel effect of a shallow patent processus. In contrast, Tam et al.⁶ considered that false-negative CPPV was the closure of the opening of CPPV by the peritoneal fold during insufflation. Although their postulations on the false-negative CPPV were not totally consistent, both groups agreed that the pneumoperitoneum pressure played an important role on CMIH development. However, there was no direct evidence concerning such a hypothesis so far. In this study, subgroup analysis indicated that high-pressure pneumoperitoneum was usually associated with a slightly higher incidence of CMIH, which supported the previous postulation.

Among the included studies, there were some variations of CPPV definitions. According to the range of definition, we classified it into a broad one and a narrow one, as described above. Obviously, there would be more false-negative CPPVs arising when detecting inconspicuous CPPVs with a narrow definition. Maddox and Smith¹⁵ classified the “cleft” of the contralateral internal ring as negative CPPV and found the incidence of CMIH deriving from negative CPPV to be as high as 5.3%. Our subgroup analysis also confirmed that the CMIH incidence was lower for using a broad definition than for using a narrow one, although there was no statistically significance.

There were many factors associated with CMIH development. We attempted to explore the factors and its possible mechanism. However, most authors in the early stage did not pay much attention to this rare phenomenon, and they did not document these critical data in their studies, such as experience of surgeon, method of laparoscopic exploration, development of abdominal wall, direction of the inguinal canal, and individual differences. So, our current analysis was not sufficient. Furthermore, we also found some inconsistent results: the CMIH incidence was higher in patients with 70° endoscopy than in those with 30° endoscopy for the transinguinal approach and lower with a pneumoperitoneum pressure of >8 mm Hg than with ≤8 mm Hg. Perhaps this was just a coincidence. However, because of the lack of data in the literature regarding CMIH development following false-negative laparoscopic evaluation for CPPV, we could not explain it at present. Therefore, more studies including full relevant data are awaited in the future.

In conclusion, CMIH following negative laparoscopic evaluation for CPPV was a rare but possible phenomenon. Choosing the transumbilical approach, transinguinal laparoscopy with large angle, low-pressure pneumoperitoneum, and broad CPPV definition would probably reduce the occurrence of such CMIHs.

Disclosure Statement

No competing financial interests exist.

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