Bilateral hydroureteronephrosis: A neonatal presentation of bladder duplication.

In a male neonate with bilateral hydroureteronephrosis, the most common surgical diagnosis is posterior urethral valves. This case report describes a male infant with the same presentation, but caused by a very uncommon congenital anomaly. The summation of different imaging modalities allowed a multidisciplinary team of colleagues to define the anatomy: bilateral duplex kidneys draining into separate urinary bladders. Only one of the bladders had an outlet, hence the obstructive uropathy to the right kidney led to total loss of function. The distended tortuous ureters produced a mass effect at presentation. This case acts as a reminder that complex congenital anomalies can mimic the presentation of more common conditions, and that they often require input from various specialists to diagnose the condition and guide its management.

Recommendations of patients and families of girls with 46XX congenital adrenal hyperplasia in the United Kingdom regarding the timing of surgery.

PURPOSE: The timing of surgery for congenital adrenal hyperplasia (CAH) is contentious. We aimed to survey expert families and patients for their recommendations regarding timing of surgery for a family with a newly diagnosed CAH child. METHODS: A Survey Monkey questionnaire was performed at the 2017 meeting of the CAH support group, "Living with CAH", and also sent to the members of the CAH support group. The surgical-timing responses were a Likert score from 1 (strongly disagree) to 5 (strongly agree). Data were analysed by Kruskal-Wallis test. p < 0.05 taken as significant. RESULTS: Of the 61 respondents, 12 were CAH patients, 43 were CAH parents, 3 were physicians, 1 surgeon and 2 others. For all respondents, the Likert score was 3 for infant, toddler and adult timing of surgery (neutral), not statistically significant (ns). For parents and/or children who had surgery (n = 26), the score was 4 (3-5) for infant vs. 4 (3-4) for toddler-years vs. 2 (1-3) for adulthood. This was statistically significant (p = 0.0002). When only patients who had CAH surgery were included, there were only 8 respondents and their scores were: infancy 3 (2-4) vs. toddler-years 4 (2-4) vs. adulthood 1 (1-4), ns. CONCLUSION: Expert families and patients in the United Kingdom who have had CAH surgery, recommend surgery in the first few years of life vs. adulthood. There is a selection bias, however this may support MDTs in continuing to discuss surgery as an option in childhood.

Tape: an alternative to stirrups or wedges in positioning for infant cystoscopy.

Performing a cystourethroscopy in children can range from reviewing a 100 kg teenage male with posterior urethritis, to assessing a 3 kg neonate with posterior urethral valves. Across this range the patient needs to be positioned in a way that allows passage of the rigid cystoscope and visualisation of the urethra and bladder. We describe a technique for positioning the legs of infants for cystoscopy using skin friendly tape, rather than wedges, stirrups or boots. The advantage of this being that it is cheap, adaptable and holds the infant in the perfect position, without needing complex equipment.

The postnatal management of boys in a national cohort of bladder outlet obstruction.

AIM: The most common cause of congenital bladder outlet obstruction (BOO) is posterior urethral valves (PUV). Initial treatment requires decompression, but transurethral incision (TUI) or primary diversion is all described. There is no randomized control trial to guide management. This study aims to describe management, circumcision, and UTI rate in a national cohort of PUV boys. METHODS: Boys diagnosed with BOO were recruited (via BAPS CASS) over 1 year with ethics committee approval (ref: 12/SC/0416). Data were collected via questionnaire, presented as number (%), analyzed by Mann-Whitney/chi-square/Fisher Exact tests, and p < 0.05 was taken as significant. RESULTS: BOO presented in 121 boys during 2014-2015, and 113 were PUV. Catheter placement in 87/121(72%) was more likely to happen in antenatal vs. postnatal vs. late(>1 y) presentations, p < 0.0001. Polyuria occurred in 23/45(51%), 12/48(25%), 0/28(0%), respectively, p < 0.0001. Initial surgical treatment was TUI in 108/121(89%) and vesicostomy in 2. Two ureterostomies were secondary procedures. Circumcision was performed in 52/121(43%) in antenatal presentation vs. postnatal vs. late 27/45(60%), 20/48(42%), 2/28(7%), respectively, p = 0.01. 69 UTIs occurred in 49 patients. Circumcision was associated with an 86% reduced risk of UTI, p < 0.0001. There was a 66% reduction in UTI risk associated with TUI alone, p < 0.01. There was 1 death due to pulmonary hypoplasia and renal failure, and 2 experienced end-stage renal failure (ESRF). CONCLUSION: Standard treatment for BOO and PUV in the current UK cohort is urethral catheterization followed by TUI. Supravesical diversion is a rescue therapy. UTIs are common and reduced by circumcision, with 43% being circumcised. Initial mortality rate was 1%, and 1.6% present in ESRF. LEVEL OF EVIDENCE: Prognostic study - Level I - Prospective National Cohort Study.

Current epidemiology and antenatal presentation of posterior urethral valves: Outcome of BAPS CASS National Audit.

AIM: Posterior urethral valves (PUVs) are the most common cause of congenital bladder outlet obstruction (BOO) in boys and end-stage renal failure (ESRF) in childhood. In the 1980s, 1 in 4000 boys had PUV. Presentation was 1/3 antenatal/neonatally, 1/3 postnatal, 1/3 late (>1 year). This study aimed to describe the current proportions in a contemporary cohort. METHODS: A national audit (BAPS CASS) of referrals in the UK and Ireland of boys diagnosed with suspected or confirmed PUV in a year was conducted. National registration data provided the male birth-rate. Data were presented as number (%), analysed by Mann-Whitney U-test and Chi-square test, with P < 0.05 taken as significant. The study was approved by a national ethics committee (NRES Committee South Central Oxford A (12/SC/0416)). RESULTS: Data were collected from 1st October 2014 to 30th September 2015 from 25/26 centres on 121 cases of suspected bladder outlet obstruction (BOO), of which 113 (93%) were because of PUV. The male birth rate during the period was 432,806/year. The calculated incidence of BOO was 1/3580 and for PUV was 1/3800 per-annum. The proportion of PUV presenting according to age was: antenatally (n = 40, 35%), infancy (n = 47, 42%), and late (n = 26, 23%). Plasma creatinine was higher in antenatally-diagnosed BOO vs. postnatal, 54 (39.5-109.5) µmol/l vs. 34(21-47) µmol/l, P = 0.0005. Hydronephrosis and ureteric dilatation were significantly greater in antenatally diagnosed BOO vs. postnatal vs. late. Renal dysplasia (cortical thinning, poor corticomedullary differentiation, or renal cysts) was significantly more likely in antenatally diagnosed BOO. CONCLUSION: Neither the incidence (~1/4000) nor the proportion antenatally diagnosed (~1/3) of boys with PUV appears to have changed in the past 30 years. Those boys who were antenatally diagnosed have significantly higher postnatal plasma creatinine, more hydroureteronephrosis, and renal dysplasia than those diagnosed in infancy or later. It may be hypothesized that this is the reason they are detected antenatally. LEVEL OF EVIDENCE: Prognosis study - Level I - prospective national cohort study.

Improving the Performance of DNA Strand Displacement Circuits by Shadow Cancellation.

DNA strand displacement circuits are powerful tools that can be rationally engineered to implement molecular computing tasks because they are programmable, cheap, robust, and predictable. A key feature of these circuits is the use of catalytic gates to amplify signal. Catalytic gates tend to leak; that is, they generate output signal even in the absence of intended input. Leaks are harmful to the performance and correct operation of DNA strand displacement circuits. Here, we present "shadow cancellation", a general-purpose technique to mitigate leak in catalytic DNA strand displacement circuits. Shadow cancellation involves constructing a parallel shadow circuit that mimics the primary circuit and has the same leak characteristics. It is situated in the same test tube as the primary circuit and produces "anti-background" DNA strands that cancel "background" DNA strands produced by leak. We demonstrate the feasibility and strength of the shadow leak cancellation approach through a challenging test case, a cross-catalytic feedback DNA amplifier circuit that leaks prodigiously. Shadow cancellation dramatically reduced the leak of this circuit and improved the signal-to-background difference by several fold. Unlike existing techniques, it makes no modifications to the underlying amplifier circuit and is agnostic to its leak mechanism. Shadow cancellation also showed good robustness to concentration errors in multiple scenarios. This work introduces a direction in leak reduction techniques for DNA strand displacement amplifier circuits and can potentially be extended to other molecular amplifiers.

Extended spectrum beta lactamase (ESBL) producing bacteria urinary tract infections and complex pediatric urology.

AIM OF THE STUDY: Extended spectrum beta lactamase (ESBL) producing bacteria are resistant to most beta-lactam antibiotics including third-generation cephalosporins, quinolones and aminoglycosides. This resistance is plasmid-borne and can spread between species. Management of ESBL is challenging in children with recurrent urinary tract infections (UTIs) and complex urological abnormalities. We aim to quantify the risk in children and specifically in urological patients. METHODS: Retrospective review of a microbiology database (April 2014 to November 2015). This identified urine isolates, pyuria, ESBL growth and patient demographics. Data analysis was by Chi square, Mann-Whitney U-test and ANOVA. A P value of <0.05 was taken as significant. MAIN RESULTS: Analysis of 9418 urine samples showed 2619 with pure isolates, of which 1577 had pyuria (>10×106 WC/L). 136 urine cultures (n=79 patients) grew purely ESBL. Overall, 5.2% of urine isolates were ESBL and 9.5% isolates with pyuria (>100×106 WC/L) had ESBL, whereas only 22/1032 (2.1%) with no pyuria, (P<0.0001). Urology patients had 86/136 (63%) ESBL positive cultures. These represented 86/315 (27%) of all positive cultures for urology patients vs. 50/2267 (2.2%) for all other specialties (P<0.0001). Potential ESBL transmission between organisms occurred in 3 (all on prophylactic antibiotics). Over the study period, there was no significant rise of the monthly incidence between 2014 and 2015 (ANOVA P=0.1). CONCLUSION: This study is the first to document the incidence of ESBL in children (5%), and estimate the frequency of possible plasmid transmission between bacterial species in children. This quantifies the risk of ESBL, especially to urology patients, and mandates better antibiotic stewardship. LEVEL OF EVIDENCE: Level IIc.

Probabilistic Analysis of Localized DNA Hybridization Circuits.

Molecular devices made of nucleic acids can perform complex information processing tasks at the nanoscale, with potential applications in biofabrication and smart therapeutics. However, limitations in the speed and scalability of such devices in a well-mixed setting can significantly affect their performance. In this article, we propose designs for localized circuits involving DNA molecules that are arranged on addressable substrates and interact via hybridization reactions. We propose designs for localized elementary logic circuits, which we compose to produce more complex devices, including a circuit for computing the square root of a four bit number. We develop an efficient method for probabilistic model checking of localized circuits, which we implement within the Visual DSD design tool. We use this method to prove the correctness of our circuits with respect to their functional specifications and to analyze their performance over a broad range of local rate parameters. Specifically, we analyze the extent to which our localized designs can overcome the limitations of well-mixed circuits, with respect to speed and scalability. To provide an estimate of local rate parameters, we propose a biophysical model of localized hybridization. Finally, we use our analysis to identify constraints in the rate parameters that enable localized circuits to retain their advantages in the presence of unintended interferences between strands.

Combined creatinine velocity and nadir creatinine: A reliable predictor of renal outcome in neonatally diagnosed posterior urethral valves.

INTRODUCTION: Nadir creatinine (lowest creatinine during the first year following diagnosis) is a recognised indicator of future chronic renal impairment (CRI) in posterior urethral valve (PUV) patients. We recently described "creatinine velocity" (Cvel), the rate of change of creatinine following initial bladder drainage, as a new early predictor of CRI in neonatally diagnosed PUV. Rising Cvel (>3 µmol/L/day) is associated with increased risk of CRI. OBJECTIVE: We studied these two prognostic indicators in combination, as a test for future CRI in neonatally diagnosed PUV patients. STUDY DESIGN: Medical records for patients treated by endoscopic valve ablation at our institution between 1993 and 2004 were reviewed. Simple linear regression was used to calculate Cvel. Creatinine velocity and nadir creatinine were considered predictive of future CRI if they were greater than 3 µmol/L/day or greater than 75 µmol/L (0.85 mg/dL), respectively. Chronic renal insufficiency was defined as CKD2 or higher. Outcomes in test groups were analysed by Fisher exact test. Statistical significance was defined as p < 0.05. RESULTS: Sixty-two patients were treated within the first 30 days of life and had sufficient data to calculate both Cvel and nadir creatinine. Mean follow-up was 9.4 years. Patients were grouped as having both risk factors (Group A), one risk factor (Group B), or neither risk factor (Group C). All four (100%) patients from Group A developed CRI, compared with 11 of 17 (64.7%) patients from Group B and three of 41 (7.3%) patients from Group C (p ≤ 0.0005). As a diagnostic test for future CRI, "presence of at least one risk factor" had a specificity of 86.4%, sensitivity of 83.3%, positive predictive value of 71.4%, and negative predictive value of 92.7%. Additional prognostic information was obtained by assigning a score from 1 to 3 for each prognostic indicator (Table). The sum of these scores gave a PUV Risk Score. No patient with a PUV Risk Score of 2 developed CRI, while all patients with a Score of 6 developed CRI. Incidence of CRI in patients with PUV Risk Scores of 3, 4, and 5 was 8.3%, 50%, and 63.6%, respectively (p ≤ 0.0005). CONCLUSION: Considered together, these prognostic indicators provide a powerful test for future CRI. Presence of at least one of these risk factors should be considered "at risk for CRI". Patients with neither risk factor are unlikely to develop CRI. Calculation of the PUV Risk Score provides an even more accurate prognosis.

Directed enzymatic activation of 1-D DNA tiles.

The tile assembly model is a Turing universal model of self-assembly where a set of square shaped tiles with programmable sticky sides undergo coordinated self-assembly to form arbitrary shapes, thereby computing arbitrary functions. Activatable tiles are a theoretical extension to the Tile assembly model that enhances its robustness by protecting the sticky sides of tiles until a tile is partially incorporated into a growing assembly. In this article, we experimentally demonstrate a simplified version of the Activatable tile assembly model. In particular, we demonstrate the simultaneous assembly of protected DNA tiles where a set of inert tiles are activated via a DNA polymerase to undergo linear assembly. We then demonstrate stepwise activated assembly where a set of inert tiles are activated sequentially one after another as a result of attachment to a growing 1-D assembly. We hope that these results will pave the way for more sophisticated demonstrations of activated assemblies.

Posterior urethral valves: creatinine velocity, a new early predictor of renal insufficiency.

AIM: Antenatal screening has led to early detection of posterior urethral valves (PUV). However, despite early intervention, a proportion of children will develop chronic renal insufficiency. We studied the trend of serum creatinine following urinary tract decompression during the neonatal period in infants as a possible predictor of chronic renal insufficiency. METHODS: Patients treated by endoscopic resection of posterior urethral valves between 1993 and 2004 were identified. From these, infants treated within the first 30 days of life were identified. Serum creatinine values taken within the first 5 days following initial drainage were recorded. A creatinine velocity for each patient was calculated by linear regression analysis. Creatinine was considered rising if velocity was >3 µmol/L/day, or falling if velocity was <-3 µmol/L/day. Chronic renal insufficiency was defined as CKD2 or higher. RESULTS: Sixty-four neonates had decompression of the urinary tract. Of these, 16 had rising creatinine despite drainage, 10 had a plateau in creatinine level, and 36 had falling creatinine following drainage. Insufficient data were available in two to calculate creatinine velocity. Progression to renal insufficiency was significantly higher in patients with an initial rise in creatinine (62.5%) than in those with plateau creatinine (40%) or falling creatinine (8.6%) (P ≤ 0.0005 by Fisher exact test). Mean follow-up was 9.2 years. CONCLUSIONS: Rising creatinine, even transiently, following urinary tract drainage in neonates with posterior urethral valves is significant and is a new and important indicator of long-term prognosis.

An autonomously self-assembling dendritic DNA nanostructure for target DNA detection.

There is a growing need for sensitive and reliable nucleic acid detection methods that are convenient and inexpensive. Responsive and programmable DNA nanostructures have shown great promise as chemical detection systems. Here, we describe a DNA detection system employing the triggered self-assembly of a novel DNA dendritic nanostructure. The detection protocol is executed autonomously without external intervention. Detection begins when a specific, single-stranded target DNA strand (T) triggers a hybridization chain reaction (HCR) between two, distinct DNA hairpins (α and ß). Each hairpin opens and hybridizes up to two copies of the other. In the absence of T, α and ß are stable and remain in their poised, closed-hairpin form. In the presence of T, α hairpins are opened by toe-hold mediated strand-displacement, each of which then opens and hybridizes two ß hairpins. Likewise, each opened ß hairpin can open and hybridize two α hairpins. Hence, each layer of the growing dendritic nanostructure can in principle accommodate an exponentially increasing number of cognate molecules, generating a high molecular weight nanostructure. This HCR system has minimal sequence constraints, allowing reconfiguration for the detection of arbitrary target sequences. Here, we demonstrate detection of unique sequence identifiers of HIV and Chlamydia pathogens.

Introduction of sodium pentosan polysulfate and avoidance of urethral catheterisation: improved outcomes in children with haemorrhagic cystitis post stem cell transplant/chemotherapy.

PURPOSE: Haemorrhagic cystitis (HC) is an uncommon but potentially devastating complication of chemotherapy and bone marrow transplantation in children. We aimed to test the hypothesis that early recognition, sodium pentosan polysulfate (SPP), and avoidance of urethral catheterisation improve outcomes in children with HC. METHODS: A retrospective case note review was performed of all patients treated for HC in our hospital from 2002 to 2010. A protocol for the management of HC was introduced in 2007 advocating early detection, use of SPP, and avoidance of urethral catheterisation. Data collected on each patient included primary condition, medications at onset, blood transfusions, duration of symptoms, catheter usage, and outcome. Statistical analysis was performed using the Mann-Whitney U test, and Fisher's Exact test as appropriate, P < .05 being significant. RESULTS: Five patients were treated using protocol with 5 historical controls. There was no significant difference between the ages of the group, diagnosis, and treatment at onset of HC. In the historical group, 4 of 5 died with HC, but all recovered in the protocol group (P < .05). Blood transfusion requirements were also significantly reduced after protocol introduction (P < .05). CONCLUSION: Early identification, avoidance of urethral catheterisation, and use of SPP significantly reduces blood transfusion requirements and mortality from HC.

Meta-DNA: synthetic biology via DNA nanostructures and hybridization reactions.

Can a wide range of complex biochemical behaviour arise from repeated applications of a highly reduced class of interactions? In particular, can the range of DNA manipulations achieved by protein enzymes be simulated via simple DNA hybridization chemistry? In this work, we develop a biochemical system which we call meta-DNA (abbreviated as mDNA), based on strands of DNA as the only component molecules. Various enzymatic manipulations of these mDNA molecules are simulated via toehold-mediated DNA strand displacement reactions. We provide a formal model to describe the required properties and operations of our mDNA, and show that our proposed DNA nanostructures and hybridization reactions provide these properties and functionality. Our meta-nucleotides are designed to form flexible linear assemblies (single-stranded mDNA (ssmDNA)) analogous to single-stranded DNA. We describe various isothermal hybridization reactions that manipulate our mDNA in powerful ways analogous to DNA-DNA reactions and the action of various enzymes on DNA. These operations on mDNA include (i) hybridization of ssmDNA into a double-stranded mDNA (dsmDNA) and heat denaturation of a dsmDNA into its component ssmDNA, (ii) strand displacement of one ssmDNA by another, (iii) restriction cuts on the backbones of ssmDNA and dsmDNA, (iv) polymerization reactions that extend ssmDNA on a template to form a complete dsmDNA, (v) synthesis of mDNA sequences via mDNA polymerase chain reaction, (vi) isothermal denaturation of a dsmDNA into its component ssmDNA, and (vii) an isothermal replicator reaction that exponentially amplifies ssmDNA strands and may be modified to allow for mutations.

Endoscopic placement of double-J ureteric stents in children as a treatment for primary obstructive megaureter.

AIM: To determine the efficacy and potential complications of double-J ureteric stents in the treatment of persistent or progressive primary obstructive megaureter in pediatric patients within our institution. MATERIALS AND METHODS: A retrospective case-note review of all patients with double-J ureteric stents, between 1997 and 2004, was performed. In all, 38 stents were inserted in 31 patients aged between 2 months and 15 years of age. Complications and results of follow-up investigations and the need for follow-up investigations were recorded. Patients were followed up clinically and radiologically for a minimum of 2 years following stent insertion. RESULTS: Endoscopic placement of double-J ureteric stents in childhood is straightforward and complications are uncommon (8/38 insertions). In non-resolving or progressive primary non-refluxing megaureter, double-J ureteric stenting alone is effective with resolution of primary non-refluxing megaureter in 66% of cases (25/38 insertions). CONCLUSIONS: Ureteric stenting provides an alternative to early surgery in patients with primary non-refluxing megaureter. The youngest patient in our series was 2 months old at the time of endoscopic ureteric double-J stent insertion. Endoscopic placement of ureteric double-J stents should be considered as a first-line treatment in the management of persistent or progressive non-refluxing megaureter leading to progressive hydronephrosis or pyonephrosis.

An audit of routine grey scale sonograghic imaging for pelviureteric junction obstruction: do they identify lower polar vessels?

BACKGROUND: Aberrant lower polar vessels are uncommon causes of pelviureteric junction (PUJ) obstruction. Preoperative identification would help in planning the appropriate procedure. We attempted to determine whether routine investigations would predict crossing lower polar vessels. MATERIALS AND METHODS: This was a retrospective study of 20 patients that either had ultrasonographic investigation by a radiologist who was blinded to the aetiology of PUJ obstruction, or underwent minimal access surgery for PUJ obstruction, from 2005 to 2007, in the Birmingham Children's Hospital, UK. RESULTS: There were 20 patients with PUJ obstruction, 8 were found at operation to have crossing lower polar vessels causing PUJ obstruction. The sonography correctly identified crossing vessels in only one, with a sensitivity of 12.5%, specificity of 66.6%, positive predictive value of 20%, and negative predictive value of 53%. CONCLUSION: Preliminary results showed that none of these investigations could reliably identify lower polar vessels.

Laparoscopic management and outcomes in non-functioning moieties of duplex kidneys in children.

AIMS: Retroperitoneal laparoscopic hemi-nephrectomy (RLHN) is a well tolerated, minimally invasive, although technically demanding, procedure for children with a non-functioning moiety in a duplex kidney. There is very little published data on the long-term follow up of such patients. We collected data to assess outcomes from our experience. METHODS: Data were retrospectively gathered on all patients who underwent RLHN at our institution between February 2003 and July 2008. Follow-up ultrasounds were obtained in all patients. RESULTS: RLHN was performed in 42 patients. All had a non-functioning moiety of a duplex kidney and in addition recurrent urinary tract infections (n=36), incontinence (n=5) or vesico-ureteric reflux (n=1). Median age at surgery was 3 years, 7 months (4 months-13 years, 10 months). One patient required conversion to open procedure due to low (pelvic) kidney. The median operating time was 90min (45-150min). Urine leak developed postoperatively in one patient and loss of function of the remaining moiety occurred in another patient. They were followed up for a median period of 11 months (1-51 months). CONCLUSION: RLHN is a feasible and safe technique for the experienced paediatric laparoscopic urologist. Results compare very favourably with open heminephrectomy in terms of operating time and outcomes. Long-term follow up is mandatory.

Retroperitoneal cystic lymphangioma: a rare presentation in childhood, treated laparoscopically.

Retroperitoneal cystic lymphangioma is a rare benign lesion of childhood. A 15-year-old girl underwent laparoscopic excision of such a cyst. On histopathological examination, the resection was complete. She had an uneventful recovery and remains asymptomatic. We report this in view of the rarity of this condition and also the unusual presentation of this case. Complete surgical excision via laparoscopy is a feasible option.

Horseshoe kidney: retroperitoneoscopic nephrectomy.

The ideal approach for nephrectomy in the child with horseshoe kidney is debatable. We present two such children who underwent nephrectomy by a retroperitoneoscopic approach. Recognition of its anatomical variation is essential in the management of horseshoe kidney. Surgery is high risk, even using a traditional open procedure, because loss of the remaining half of the kidney is catastrophic.

Congenital ureteric strictures: an uncommon cause of antenatally detected hydronephrosis.

Often misdiagnosed as primary megaureter or pelviureteric junction obstruction, congenital ureteral stenosis and valves are the main causes of congenital ureteric obstruction. We report three consecutive cases of congenital ureteric strictures presenting with antenatally diagnosed hydronephrosis. Two of our cases had a contralateral multicystic dysplastic kidney. We discuss the aetiology, clinical presentation, diagnostic evaluation, surgical management, and operative results as well as present an overview of the international literature, highlighting the importance of early referral in cases of contralateral abnormality as well as the importance of performing a retrograde study to facilitate the diagnosis and choice of incision.