Occurrence of abdominal bulging and hernia after open partial nephrectomy: a retrospective cohort study

Abstract

Objective: Abdominal bulging and incisional hernia are known sequelae after open partial nephrectomy (OPN) via a flank incision. Precise rates are not known. The aims of this study were to determine the rates of bulging and hernia after OPN, and to examine potential risk factors.

Materials and methods: A retrospective review was undertaken of 197 consecutive patients operated on with OPN via a flank incision between 2004 and 2014. After exclusion, 184 patients remained. Medical records and radiological images from the preoperative work-up, and follow-up after surgery at 3, 12 and 24 months, were reviewed.

Results: A visible bulge was noted in 36 of the 184 patients at clinical examination. Only 20 cases (12%) remained at the last follow-up. Radiological changes interpreted as a bulge were initially seen in 50 patients, while only 35 (19%) remained at the last radiological examination. Clinical incisional hernia was reported in five patients (3%), and radiological hernia was seen in 10 patients (5%). Patients who developed a hernia had a higher body mass index (30 vs 26 kg/m², p = 0.02). Other demographic variables showed no significant correlation.

Conclusions: Bulging is a common sequela after flank incision. The rate of incisional hernia after flank incision is comparable to rates after other forms of abdominal surgery. Further studies are required to evaluate the psychological and physiological effects of bulging, the pain and weakness caused, and the cosmetic embarrassment suffered by the patient.

Keywords:

• Bulge
• flank incision
• incisional hernia
• open partial nephrectomy
• renal cell carcinoma

Introduction

Around 1000 cases of renal cell carcinoma (RCC) are diagnosed each year in Sweden, representing 2% of all cancer diagnoses. Approximately half of these are T1 tumours where the recommended treatment is surgery [1]. The surgical methods used are radical nephrectomy (RN) or partial nephrectomy (PN), which may be performed as open, laparoscopic or robot-assisted surgery. For patients with RCC, European Association of Urology (EAU) and American Urological Association (AUA) guidelines recommend PN rather than RN whenever feasible [1,2]. PN is mandatory if one is to spare renal function in a patient with an anatomical or functional single kidney, or if the patient has decreased renal function or is at risk of renal failure [1].

While open partial nephrectomy (OPN) and laparoscopic partial nephrectomy (LPN) have comparable functional and oncological outcomes [3,4], OPN is still the main procedure for PN of RCC in Sweden. Traditional LPN and robot-assisted PN require special training and expensive equipment, and the risk of disturbed renal function is greater owing to longer periods of warm ischaemia time. The proportion of patients undergoing PN for RCC, however, has increased in Sweden; in 2005, 22% of T1aN0M0 RCCs underwent PN and in 2012 the figure was 56%. Recent years have seen an increase in the proportion of procedures performed with minimally invasive surgery [5–9].

OPN can be performed using a retroperitoneal or a transperitoneal approach. The retroperitoneal approach is performed via a flank incision between the eleventh and twelfth ribs or beneath the twelfth rib. The incision is usually 10–15 cm long, but varies depending on the surgeon’s preference and hand size, the level of exposure necessary and the amount of subcutaneous fat. A flank incision provides excellent exposure of the kidney with minimal disturbance of abdominal viscera. There are, however, concerns regarding this technique since the incision can inflict damage on the nerves in the area [10].

The twelfth thoracic (subcostal) nerve runs inferior to the twelfth rib, and it, along with the eleventh intercostal nerve, provides the abdominal wall with motor and sensory innervation [11,12]. Damage to these nerves during surgery via a flank incision can be caused by division, retractor pressure, a suture or compression by fibrous tissue during the wound healing process. Nerve damage causes paraesthesia, pain and muscle denervation, the last of these leading to muscle atrophy and bulging of the abdominal wall. There is little in the literature regarding the rate of bulging after flank incision or the patient’s perception of deformity and symptoms, nor is there an accepted system for describing the degree of bulging. The rate of bulging has previously been reported to be 19–57% after both retroperitoneal aortic repair and OPN, both procedures using a flank incision in the eleventh intercostal space or below the twelfth rib [13–16]. Incisional hernia also occurs after flank incision, although little is known of its frequency.

The aim of this study was to determine the rates of bulging and incisional hernia after OPN via a flank incision, and to assess the potential risk factors involved.

Materials and methods

Patients

The initial cohort was a group of 197 consecutive patients treated with OPN via a flank incision between 2004 and 2014. Of these, 169 were treated at Umeå University Hospital (NUS) and 28 at Sundsvall-Härnösand Regional Hospital (SHH). Patient records were scrutinised for demographic data [age at surgery, gender, body mass index (BMI)], medical history (smoking, diabetes, previous hernia), laboratory tests (preoperative erythrocyte sedimentation rate, C-reactive protein, plasma albumin, haemoglobin), surgical data (tumour size, side of surgery, operating time, estimated blood loss, postoperative complications, length of postoperative hospital stay) and pathology data.

Records from each follow-up, at 3, 12 and 24 months, were scrutinised to evaluate the rates of abdominal bulging and/or hernia, as described in the records by the surgeon examining the patient. In the clinical setting, bulging is usually assessed by clinical examination of the patient in the standing and supine positions. Preoperative and follow-up data were entered into a database for statistical analysis.

Thirteen patients were excluded; three underwent surgery with a transperitoneal approach, five had no recorded follow-up, two were followed up once but abdominal status could not be ascertained from the records, two were lost to follow-up and one patient died in the postoperative period. Thus, 184 patients remained eligible for the study, 158 from NUS and 26 from SHH.

Radiological grading

Reports from routine follow-up computed tomography scan, in the supine position without Valsalva manoeuvre, were reviewed for the presence of bulging or hernia. A bulge was defined as a protrusion with deformity of the abdominal wall that did not have a complete defect in its thickness in the muscle wall. The degree of bulging was assessed from the images and graded on a scale from 1 to 4, where 1 was ‘no bulge’ and 4 ‘severe bulging’, i.e. a deforming bulge spanning the entire length of the abdominal wall. The presence of a hernia was defined as a complete defect in the muscle wall with protrusion of abdominal viscera.

Statistical analyses

Patients were divided into three groups for the purpose of statistical analysis: patients with (i) bulge or (ii) hernia, and (iii) patients with neither of these. Statistical analyses, using STATA/IC 13.1, were performed for clinical outcome and radiological outcome separately. Categorical variables were tested with the chi-squared or Fisher’s exact test. The t test and Wilcoxon rank sum test were used to compare parametric and non-parametric variables, respectively.

Results

All 184 patients had a preoperative radiological image, and 158 (85.9%) had at least one radiological follow-up at 3, 12 or 24 months. Loss to radiological follow-up was mostly caused by patients with benign tumours where there was no need for follow-up. Of the 184 patients, 175 (95.1%) had at least one recorded clinical follow-up after surgery. Sixty-nine patients (37.5%) had one follow-up after surgery, 41 (22.2%) had two follow-up visits and 65 (35.3%) had three follow-up visits. Loss to the study in this category was caused by patients moving to or living in another county and follow-up being carried out there instead, patients with a benign tumour who cancelled their follow-up or patients otherwise unable to attend a follow-up visit. In 10 cases, records of abdominal status from clinical follow-up were missing. The number of patients with adequate clinical information was thus 167 (90.8%). Table 1 shows the number of patients and the rates of bulging and hernia at each follow-up.

Table 1. Rates of clinical and radiological bulging and hernia at each follow-up.

	3 Months	12 Months	24 Months
Clinical follow-up	165	106	75
Bulging	38 (23.0)	11 (11.1)	2 (2.7)
Hernia	1 (0.6)	3 (2.8)	3 (4.0)
No. of follow-up visits attended
One (n = 69)	62	7	0
Two (n = 41)	38	34	10
Three (n = 65)	65	65	65
Radiological follow-up	117	128	105
No bulge	67	81	64
Slight bulging	27	20^c	18
Moderate bulging	9	12	10
Severe bulging	4^b	3^c	3
Bulging total	40 (34.2)	35 (27.3)	31 (29.5)
Hernia	3^b (2.6)	9^c (7.0)	5 (4.8)
Could not be assessed^a	8	5	5

Data are shown as n or n (%).

^a Image where presence of bulge or hernia could not be assessed; ^bone patient with both hernia and bulge; ^ctwo patients with both hernia and bulge.

There were no statistical differences in bulging or hernia when comparing the high-volume centre (NUS) with the low-volume centre (SHH). Table 2 shows demographics and comparisons between hospitals.

Table 2. Demographics and differences between hospitals.

	Overall	NUS	SHH	p
n	184	158	26
Male	119 (64.7)	104 (65.8)	15 (57.7)	0.42
Right-sided surgery	95 (51.6)	83 (52.5)	12 (46.2)	0.55
Age (years)	64.7 (63.0–66.4)	65.3 (63.5–67.0)	61.1 (55.9–66.3)	0.12
BMI (kg/m^2)	27.6 (26.9–28.3)	27.7 (26.9–28.5)	26.9 (25.1–28.7)	0.38
Malignant tumour	137 (74.5)	120 (76.0)	17 (65.4)	0.25
Clinical follow-up	167 (90.1)	141 (89.2)	26 (100)	0.08
Clinical bulge	20 (10.9)	17 (10.8)	3 (12.0)	0.95
Radiological follow-up	158 (85.9)	137 (86.7)	21 (80.1)	0.38
Radiological bulge	35 (22.2)	28 (20.4)	7 (33.3)	0.10
Radiological hernia	10 (6.3)	7 (5.2)	3 (11.5)	0.09

Data are shown as n, n (%) or mean (95% confidence interval).

NUS: Umea University Hospital; SHH: Sundsvall-Härnösand Regional Hospital; BMI: body mass index.

Clinical bulging was reported in 36 patients (19.6%) at follow-up, although only 20 (12.0%) had a bulge at the final follow-up. Fifty patients (27.7%) had abdominal bulging radiologically, but only 35 bulges (19.0%) were seen on the last recorded radiological image. The results of analyses of risk factors for clinical and radiological bulge are shown in Tables 3 and 4, respectively. Five patients (2.7%) had a hernia documented at clinical follow-up and 10 patients (5.4%) had a hernia radiologically. There was discrepancy between the rate of clinical bulge and that of radiological bulge (Tables 5 and 6). Of the 36 patients who had a clinical bulge at the first examination, 10 had no radiological bulge. These 10 patients were only evaluated clinically at the 3 month follow-up.

Table 3. Comparison of patients with persistent clinical bulge versus patients without clinical bulge or hernia.

	No clinical bulge or hernia (n = 142)	Persistent clinical bulge (n = 20)	p
Male	93 (65.5)	11 (55.0)	0.36
Right-sided surgery	73 (51.4)	10 (50.0)	0.91
Age (years)	66 (57–74)	70 (60–75)	0.35
BMI (kg/m^2)	26 (24–29)	27 (25–31)	0.17
Malignant tumour	111 (78.2)	11 (55.0)	0.02
Duration of surgery (min)	154 (120–197)	178 (126–225)	0.36
Blood loss during surgery (ml)	200 (100–400)	350 (200–500)	0.05
Postoperative care (days)	6 (4–8)	6 (5–7)	0.67
Plasma albumin (g/dl)	43 (41–45)	43 (42–46)	0.17
ESR (mm/h)	13 (6–20)	8 (4.5–16.5)	0.15
β-Haemoglobin (g/l)	139 (126–147)	143.5 (134.5–151.5)	0.17

Data are shown as n (%) or median (interquartile range).

BMI: body mass index; ESR: erythrocyte sedimentation rate.

Table 4. Comparison of patients with persistent radiological bulge versus patients without radiological bulge or hernia.

	No radiological bulge or hernia (n = 113)	Persistent radiological bulge (n = 35)	p
Male	74 (65.5)	22 (62.9)	0.78
Right-sided surgery	58 (51.3)	22 (62.9)	0.23
Age (years)	66.3 (57.7–73-0)	65.4 (59.6–72.4)	0.96
BMI (kg/m^2)	26 (24–29)	27 (25–31)	0.13
Malignant tumour	94 (83.2)	30 (85.7)	0.72
Duration of surgery (min)	162 (120–197)	160 (124–212)	0.64
Blood loss during surgery (ml)	200 (100–500)	300 (100–850)	0.38
Postoperative care (days)	6 (4–7)	6 (4–9)	0.66
Plasma albumin (g/dl)	43 (41–45)	43 (42–44)	0.66
ESR (mm/h)	11 (6–23)	13 (6–18)	0.88
β-Haemoglobin (g/l)	140 (127–147)	141 (128–147)	0.86

Data are shown as n (%) or median (interquartile range).

BMI: body mass index; ESR: erythrocyte sedimentation rate.

Table 5. Degree of bulge on last reviewed radiological image versus occurrence of bulge at last clinical follow-up.

	Radiological images
	No bulge	Slight bulging	Moderate bulging	Severe bulging
No clinical bulge	85	19	7	3
Clinical bulge	9	1	2	1

Table 6. Distribution of patients according to method of diagnosing the bulge.^a

	Clinical evaluation
CT	No bulge	Bulge	Unknown	Total
No bulge	90	10	13	113
Bulge	27	4	4	35
Unknown	21	5	0	26
Total	138	19	17	174

^a Patients with hernia (n = 10) excluded.

CT: computed tomography.

Eleven of the 50 patients with initial radiological bulging showed an improvement in the degree of bulging, where nine had no bulge (degree 1) on their last reviewed radiological image, and two had decreased from degree 4 to degree 3. Bulging became worse in only one patient, increasing from degree 2 at the 3 month follow-up to degree 4 at the subsequent follow-up visits 12 and 24 months after surgery.

Ten patients developed a hernia; five were diagnosed both clinically and radiologically, four were seen on radiological images but had no clinical record of hernia, and one patient had a clinical bulge but radiologically it was shown to be a hernia.

No significant risk factor was seen when comparing patients with clinical bulge with those without bulge or hernia, although malignant tumour (p = 0.05) and blood loss during surgery (p = 0.07) showed a tendency towards significance.

Among the patients who developed a hernia, BMI was a significant risk factor (median 30 kg/m² in the hernia group vs 26 kg/m² in patients without hernia or bulging, p = 0.02).

Thirty-three wound complications in 29 patients were noted in the records; 16 developed a haematoma, 13 a wound or deep infection, three had superficial wound dehiscence and one had a seroma. Four of these 29 patients developed clinical bulging, and one developed a hernia. These numbers were too small to obtain any statistical relevance. When all patients with a surgical complication were grouped together and compared with those without, no significant difference in the rates of bulging or hernia was found.

Discussion

Today, OPN via a flank incision is the most common surgical procedure for small renal masses. This study evaluated the rates of bulging and hernia following this technique. Few studies have considered the topic of bulging, and its mechanism of development, rates and risk factors. Previous studies have shown rates ranging from 19% to 57% [13–16], while the present study had overall rates of 20% for clinical bulging, 10% for persistent clinical bulging and 19% for persistent radiological bulging. Bulging is thus a common sequela following OPN via a flank incision. Of the patients included in this study, 14.1% had no radiological follow-up, which could have led to underestimation of the rate of radiological bulging.

In this cohort, almost half of the patients who had a clinical bulge at the first follow-up (n = 34) had no bulging at subsequent examinations. Nineteen patients had a bulge at their only clinical examination, but some of these bulges may have been transient since there is no later known information. Data from the latest recorded follow-up were used, which could be a source of error.

Clinically, two types of bulging were observed: patients with a bulge at 3 months that was no longer present at subsequent follow-up, and those who developed a bulge that was still visible at 24 months. This could be explained by different mechanisms of development; the lasting bulge could be caused by complete nerve injury, such as division at surgery, and the transient bulge could be caused by either pressure on the nerve during surgery or postoperative swelling of tissue compressing the nerve.

There have been few studies on the consequences of having a bulge. Chatterjee et al. showed that some patients complained of pain from the bulge, and clinical experience has shown that a bulge is cosmetically disturbing [13]. It is possible that a weakened abdominal wall could affect postural stability, leading to the development of chronic lower back pain. Further studies are required to evaluate in greater detail the consequences of bulging.

This study evaluated potential risk factors for developing an abdominal bulge. No significant differences between patients with and those without a bulge were found. Matsen et al. [15] showed a higher frequency of bulging in patients with high BMI, whereas Crouzet et al. [14] suggested that in cases of obesity it is more likely that the incision is extended anteriorly to improve exposure, with increased risk of nerve injury. Incision extension, however, was rare in the present patient material, and this could explain why no difference in BMI was seen between groups with regard to bulging. This material was somewhat small, especially when dividing the cohort into different categories and between hospitals. This was a retrospective study and the data were somewhat limited, making statistical significance difficult to achieve when dealing with smaller differences between samples. However, the results give an indication of the rate of bulging after flank incision, and based on this it will be possible to calculate power and sample size in future prospective studies.

Clinical experience shows hernia to be less of a problem after flank incision than bulging. Hernia, however, may have more serious consequences for the patient, such as the risk of strangulation. The rate of hernia was 5% in this study, which is similar to rates after other forms of abdominal surgery (2–20%) [17].

The BMI in this study was found to be higher in the group that developed an incisional hernia. High BMI is a known risk factor for the development of hernia after other forms of abdominal surgery, partly owing to a higher intra-abdominal pressure [17]. Patients with high BMI may also have a different matrix metalloproteinase composition, leading to an increased risk of hernia formation [18].

Flank hernia repair is complicated by the fact that the most commonly used technique for other incisional hernias, i.e. preperitoneal sublay, is not possible. The intraperitoneal overlay mesh technique is the most commonly used, but this is complicated and requires the use of a very large mesh. The use of prophylactic mesh in high-risk patients undergoing PN is an alternative, but remains to be evaluated in a randomised study. As seen in this study, high BMI is a risk factor for incisional hernia, and the use of prophylactic mesh implantation in obese patients may thus be advantageous.

Owing to the risk of abdominal bulge and incisional hernia following flank incision, other surgical techniques for the treatment of RCC should be considered. Since minimally invasive methods, such as laparoscopic or robot-assisted PN, have a similar oncological outcome, a less invasive approach should be used to minimise the risk of postoperative bulging and hernia. The disadvantage of minimally invasive surgery is the increased risk of complications during the perioperative period [19]. Such surgical strategies are recommended in RCC treatment guidelines [1]. However, the open surgical approach will continue to be used for large and complex kidney masses. When using a flank incision, it is imperative to avoid nerve damage.

Radiological follow-up was not carried out in 14.1% of patients, mainly because there was a benign histology report where follow-up was deemed unnecessary. As a result, the rates of radiologically defined bulge and hernia in this group cannot be determined.

Another question is whether 24 months’ follow-up is long enough to detect all patients who eventually develop bulging or hernia. In the present study, all patients who had a bulge at 12 or 24 months already had one at the 3 month follow-up. This suggests that it is unlikely that a new bulge would have developed after 2 years. Previous studies have shown large variations in the period between primary surgery and the development of an incisional hernia. Höer et al. found that 31.5% of incisional hernias had developed by the first 6 months and 75% had developed within 2 years after surgery [20]. Although the hernia rate in this study is comparable to rates following other forms of abdominal surgery, it is possible that the follow-up was too short to reveal all potential hernias.

The main weaknesses of this study are its retrospective design and the fact that no structured clinical follow-up, aimed at detecting bulging or hernia, was conducted. A further limitation is that follow-up visits were attended by different surgeons, and that patients had one, two or three follow-up visits. However, although radiology was not performed with the purpose of detecting bulging or hernia, i.e. no provocative measures were taken to maximise protrusion, evaluation of bulging or hernia was not affected by the study design. Furthermore, compared to a hernia, bulging is difficult to distinguish radiologically as there is no complete defect in the muscle wall and no neck, and thus no protrusion of intra-abdominal content.

In conclusion, although somewhat limited by missing data, the present study has shown that bulging is a common sequela after flank incision for renal surgery, with a persistent clinical bulging rate of 10%. The rate of incisional hernia in this study was similar to or slightly less than rates seen after other forms of abdominal surgery. Further studies are required to evaluate the psychological and physiological effects of bulging, the degree of pain and muscle weakness caused, and the cosmetic embarrassment suffered by the patient.

Acknowledgement

We thank Dr Peter Cox for providing language help.

Disclosure statement

No potential conflict of interest was reported by the authors.