2Early and late proctologic complications of delivery prevention and treatment
3The earliest evidence of severe perineal injury mummy of Henhenit, 22 yrs old Egyptian woman with rupture of the vagina into the bladder and the lower bowel was found protruding from the anus.The earliest evidence of severe perineal injury mummy of Henhenit, an Egyptian woman approximately 22 years of age from the harem of King MentuhotepII of Egypt in 2050 BC. Henhenit’s pelvis was an abnormal shape, there was a rupture of the vagina into the bladder and the lower bowel was foundprotruding from the anus. These severe perineal injuries may have been due to cephalo-pelvic disproportion that probably resulted in her earlyDeath.
5PF Muscle Stretch during Labour During 2nd stage the PF muscles stretch x 2-3 of their lengthMaximal stretch tolerated by nonpregnant animal muscle tissue = 1.5(a) Simulated effect of fetal head descent on the levator ani muscles in the second stage of labor. At top left, a left lateral view shows thefetal head (as a sphere) located posteriorly and inferiorly to the pubic symphysis (PS) in front of the sacrum (S). The sequence of fiveimages at left shows the fetal head as it descends 1.1, 2.9, 4.7, 7.9, and 9.9 cm below the ischial spines while the head passes along thecurve of Carus (indicated by the transparent, light blue, curved tube). The sequence of five images at right are front-left, three-quarterviews corresponding to those shown at left. (b) The upper bar graph compares, by muscle, initial and final muscle lengthscorresponding to 1.1 and 9.9 cm model fetal head descent, respectively. The lower bar graph shows the maximum correspondingstretch ratio found in each levator ani muscle band. Note that the value of the stretch ratio is not simply proportional to initial or finallength. For both graphs, muscles are arranged left to right, in ventral to dorsal order of origin location. (c) The relationship betweenfetal head descent (abscissa, icons at top) and the resulting muscle stretch ratios (ordinate) in selected levator ani muscles. The labels atright identify the pubovisceral (PC), iliococcygeus (IC), and puborectalis (PR) muscle bands. The largest stretch is induced in themedial-most pubovisceral (PC2) muscle, the last muscle to be engaged by the fetal head. The shaded region denotes the values ofstretch tolerated by nongravid appendicular striated muscle without injury.
6Sequelae of Childbirth Perineal problemsPerineal pain, perineal haematoma, perineal wound InfectionBowel problemsAnal Fissure, haemorrhoids, constipationPelvic Organ ProlapseCystocele, uterine prolapse. Enetrocele , rectocele, rectal mucosal or complete prolapse, descent of PFIncontinenceUrinary, fecal (gas, liquid or solid stools)Recto-vaginal Fistula
7Pelvic Organ Prolapse Injury to the pelvic floor during childbirth number of vaginal deliveriesmacrosomic infantO’Boyle et al: the POPQ stage signifcantly higher in the third than in the first trimesterAssociated co-Risk factorsdefective collagenraceadvancing ageHysterectomychronic raised intra-abdominal pressure
8Childbirth and Pelvic Organ Prolapse Women’s Health Initiative:single childbirth associated with raised odds of:Uterine prolapse (odds ratio 2.1; 95% CI 1.7–2.7)Cystocoele (2.2; 1.8–2.7)Rectocele (1.9; 1.7–2.2)Every additional delivery increased the risk of worsening prolapse by10–20% (Hendrix, Am J Obstet Gynecol 2002).
9Obstructed Defecation Alterations of anatomic morphology
10Obstructed Defecation Syndrome Obstructed Defecation Syndrome (ODS) is defined as the normal desire to defecate, but an impaired ability to satisfactory evacuate the rectum
16Symptoms Straining too much and repeatedly Long standing in toilet Frequent calls to defecateAssisted defecationIncomplete evacuationFragmeted defecationPelvic pressureRectal discomfortPerineal painLaxative or enema userLack of continenceMucorreaWorsen Quality of Life
22Anal sphincter rupture is highly associated with fecal incontinence
2385% perineal trauma 69% stitches McCandlish R et al, Br J Obstet Gynaecol 1998
24Fecal Incontinence and Parturition Anal sphincter defects occur at first delivery• Primips: Before 0% After 35%• Multips: Before 40% After 44%Incontinence associated with defect: p=0.0003• 23% with defects had postpartum incontinenceSultan et al. NEJM 325:1905;1993
25Childbirth & Fecal Incontinence 259 consecutive women delivered single unit31 elective CS no FIPrimaparous delivered vaginally 13% FIAbromowitz Dis Colon Rectum 2000549 prospective fecal urgencyvag 7.3% vs CS 3.1%Chaliha 99 Obstet Gyn
26Anal Endosonography before and after Delivery in a Primiparous Woman with a Postpartum Defect of the External Anal SphincterAbdul H. Sultan et al, NEJM, 1993
28MRI defects in parous womnen Unilateral Figure 2.Axial and coronal images from a 34-year-old incontinent primiparous woman showing aunilateral defect in the left pubovisceral portion of the levator ani muscle. The arcuate pubicligament (A), urethra (U), vagina (V), rectum (R), and bladder (B) are shown. The locationnormally occupied by the pubovisceral muscle is indicated by the open arrowhead in axial andcoronal images +1.0, +1.5, and +2.0.Figure 3.Axial and coronal images of a 38-year-old incontinent primiparous woman are shown. Thearea where the pubovisceral portion of the levator ani muscle is missing (open arrowhead)between the urethra (U), vagina (V), rectum (R), and obturator internus muscle (OI) is shown.The vagina protrudes laterally into the defects to lie close to the obturator internus muscle. A= arcuate pubic ligament
30Suture or not suture 1. First degree, superficial – skin and subcutaneous tissue– vaginal mucosa– combination of the (multiple superficial lacerations)2. Second degree, deeper– superficial perineal muscles (B. spongiosus, T. perineal)– perineal body.vaginal birthSuture or not sutureless trauma next deliverless pain and infectionthe wound heals fasterunacceptable aestheticsImpaired sexual functionImpaired PF muscle strength Incontinence and prolapse
31Inadequate anatomy training Identifying 3rd degree tears Doctors 91% 60% Midwives 84% 61% . Sultan et al. NEJM, 1993
39Postoperative management AntibioticsBladder catheterisationAnalgesiaStool softenerPatient information
40Midline episiotomy is highly associated with anal sphincter rupture Sphincter rupture rate• No episiotomy: %• Episiotomy: %Thacker. Ob Gyn Survey 38:332;1983Zetterstrom. Obstet Gynecol 94:21;1999Hartmann K et al. JAMA 293(17):2141-8;2005Fitzgerald for PFDN, Obstet Gynecol 109:29;2007
41associated with sphincter rupture Operative delivery isassociated with sphincter ruptureSphincteric RuptureOdds Ratio (p value)Forceps delivery (p<0.001)Episiotomy (p<0.001)OP position (p=0.002)Vacuum delivery (p=0.001)Fitzgerald MP for PFDN, Obstet Gynecol 109:29;2007
44Interventions to Prevent Obstetrical Perineal Trauma Planned Caesarean vs. Planned Vaginal BirthExercise in PregnancyAntenatal Pelvic MassagePosition during Labor and BirthEpidural vs. Narcotics Pain ReliefEarly vs. Delayed PushingSecond stage pushing adviceSpontaneous vs. Forceps birthWater Birth
45Asymptomatic WomenAsymptomatic women who have minimal compromiseof their anal sphincter function (satisfactorypressure measurements and ultrasoundimages) should be allowed to have a vaginal delivery.These women should be counselled that they have a 95% chance of notsustaining recurrent OASIS9 or developing de novo anal incontinencefollowing delivery.68 However, the delivery should be conducted by anexperienced doctor or midwife.If an episiotomy is considered necessary, e.g.because of a thick inelastic or scarred perineum,a mediolateral episiotomyshould be performed.There is no evidence that routine episiotomiesprevent recurrence of OASIS.The threshold at which these women may be considered for a CSmay be lowered if a traumatic delivery is anticipated, e.g. in the presence of one or more additional relative risk factors such as a big baby, shoulder dystocia, prolonged labour, diffi cult instrumental delivery. However,
46symptomatic womenAll symptomatic women are first treated conservativelyConservative management of anal incontinenceis described in detail in Chapter 11 and is summarisedas follows:• All women are included in the biofeedback programme(Chapter 11).• If muscle contractility is weak or absent, electricalmuscle stimulation is commenced.• Women with flatus incontinence are givendietary advice, especially the avoidance of gasproducingfoods such as legumes.• Women with faecal incontinence are commencedon a low residue diet and constipatingagents such as loperamide can be used.
47Women whose symptoms are adequately controlled by conservative measures are offered CS inany subsequent delivery so as to minimise the riskof further compromise to anal sphincter function.Women with faecal incontinence in whom conservative measures have failed should be offered anal sphincter surgery (Chapter 12A), whileothers may need advanced surgical techniques asdescribed in Chapter 12B. All women who haveundergone successful incontinence surgery shouldbe delivered by CS.A management dilemma arises in women who suffer from faecal incontinence but who wish further pregnancies. These women could avoid aCS and undergo a vaginal delivery followed by a secondary sphincter repair at a later date. The only rationale behind this is that most of thedamage that occurs during childbirth occurs with the first vaginal delivery68,70 and therefore the risk of further damage during a subsequent vaginaldelivery is relatively small. However, there is a potentially unquantifi ed risk of deteriorating pudendal neuropathy.
48The Effect of Pregnancy Hormones on Connective Tissue Connective tissue in the area of the urogenital organs is sensitive to hormones. During pregnancy, collagen is depolymerized by placental hormones, and the ratios of the glycosaminoglycans change. (The term ‘proteoglycans’ is used here interchangeably with ‘glycosaminoglycans’.) The vaginal membrane becomes more distensile, allowing dilatation of the birth canal during delivery. There is a concomitant loss of structural strength in the suspensory ligaments. This explains the uterovaginal prolapse so often seen during pregnancy. Laxity in the hammock may remove the elastic closure force, causing urine loss on effort. This condition is described as stress incontinence. Loss of membranous support may cause gravity to stimulate the nerve endings (N) at the bladder base, so causing premature activation of the micturition reflex, expressed as symptoms of ‘bladder instability’. This condition is perceived by the pregnant patient as frequency, urgency and nocturia. Laxity may also cause pelvic pain, due to loss of structural support for the unmyelinated nerve fibres contained in the posterior ligaments. The action of gravity on these nerves causes a ‘dragging’ pain. Removal of the placenta restores connective tissue
49Following the advent of endoanal ultrasound (see Chapter 10), Sultan et al.14 demonstrated that 33%of women sustained “occult” OASIS that were notidentifi ed at delivery (see Chapter 8 for pathophysiology).Prospective studies11 have identifi ed“occult” injuries ranging between 2015 and 41%.occult or in fact unrecognised at delivery.It was alarming to find that 87% and 27% ofOASIS were not identified by midwives anddoctors respectively.
50Lal et al.20 showed thatsignifi cantly more women develop anal incontinencefollowing a second degree tear than with anintact perineum (23% vs 3%, P = 0.01).Benifl a etal.21 identifi ed a 16-fold increase in anal incontinencefollowing a second degree tear (P < 0.05).Both these studies support the fi ndings of Andrewset al. that a large number of OASIS were undiagnosedand wrongly classifi ed as second degreetears.
51Faltin et al.22 randomised 752 primiparous women with second degree lacerations to conventional examination (control group) and additional postpartum endoanal ultrasound (experimental group) and demonstrated that a considerable number of women have full-thickness OASIS that are not recognised at delivery. However, they excluded partial-thickness sphincter tears from their study. On identifying new injuries in the experimental group, a formal sphincter repair was performed. Overall, severe faecal incontinence was signifi cantly reduced from 8.7% in the control group to 3.3% in the experimental group.
52The morbidity associated with perineal injury related to childbirth constitutes a major health problem, affecting millions of women worldwide.In the UK, up to 44% of women will continueto have pain and discomfort for 10 days followingbirth3 and 10% of women will continue to havelong-term pain at 18 months postpartum.4 Furthermore,23% of women will experience superfi -cial dyspareunia at 3 months postpartum;5 up to10% will report faecal incontinence6 and approximately19% will have urinary problems.7 The ratesof complications reported by women depend onthe severity of perineal trauma
53A treatment during pregnancy is usually limited to emergency care, consisting of palliation for symptomatic prolapsing internal hemorrhoids, temporizing sclerosing injections for bleeding hemorrhoids, incision and expression of painful external anal thromboses and drainage for the relatively uncommon perianal abscess.
54The first description of rectal prolapse is said to be in the Ebers papyrus 1500 BC. The first treatment as outlined byHippocrates involved hanging patients by their heels andshaking them.10 Obviously, this was rarely successful in thelong term.The true incidence of rectal prolapse (mucosal orcomplete) is unknown mostly because of underreporting.It is associated with long-standing constipation, chronicstraining, pregnancy, prior surgery, female gender, aging,neurologic disease, mental illness (up to 53% in a study byVongsangnak et al.), and other pelvic floor disorders.11,12
55Obstetric trauma is the most important etiologic factor in the pathogenesis of fecal incontinence in women. Thereis evidence that hormonal changes during pregnancy lead to smooth muscle relaxation attributed to progesterone.Relaxin is an ovarian hormone that peaks late during pregnancyand leads to connective tissue remodeling in the pelvic floor.23 With parturition, there is stretching of the levators, stretching and tearing of the rectovaginal septum,stretching of the vaginal wall, and compression of the pudendal nerves against the pelvic side wall. All these factors may contribute to fecal incontinence.A published study by Sultan et al.24 revealed anal sphincter defects in 30% to 40% of asymptomatic postpartum females. Fortunately, the minority of these patients were symptomatic (32%). However, these patients may becomesymptomatic later in life or with subsequent vaginal deliveries.In addition, pudendal nerve injury documented by electromyography has been demonstrated in 42% of postpartum females by Snooks et al.25,26 Sixty percent of these patients recovered nerve function 2 months after delivery, but 40% did not. Four percent of 906 postpartum women in a study by MacArthur et al.27 reported new symptoms of incontinence after childbirth. Sultan et al.28 showed a 1%incidence of frank fecal incontinence and a 25% incidenceof decreased flatal control at 9 months’ follow-up after vaginal delivery.
56The incidence of sphincter injury is higher in patients with perineal tears. Up to 25% of patients developed fecalincontinence symptoms after a third degree tear in a studyby Wood et al.29 Third degree tears, involving the sphinctermuscle, occur in approximately 0.6% of all vaginal deliveries. Episiotomies, similar to tears, are associated with incontinence.Sultan et al.31 found episiotomy to be associatedwith an increased risk of sphincter injury. Signorello et al.33showed a threefold increase in fecal incontinence aftermidline episiotomy as compared with spontaneous laceration;therefore, a mediolateral episiotomy is recommended3
57Perineal pain is a common symptom following vaginal delivery, regardless of the presence ofperineal trauma. However, the severity ofperineal pain is directly proportional to the severityof perineal trauma.5,15 Perineal pain occurs in42% of women immediately after delivery but significantly reduces to 22% and 10% at 8 and 12weeks respectively. Compared to a normal delivery,perineal pain occurs more frequently andpersists for a longer period after assisted delivery(forceps, vacuum delivery, vaginal breech delivery).
61Perineal Haematoma1 : 500 and 1 : 900 vaginal deliveries.swellingpain,restlessness,inability to pass urinerectal tenesmus within a few hours after deliveryShock in sopraelevator hematomasinfralevator (vulval, perineal,vaginal)supralevator (in the broad ligament or paravaginal area)frequently after an episiotomyBut about 20% of cases in apparently intact perineumA supralevator haematoma forms in the broadligament and could be due to an extension ofa tear of the cervix, vaginal fornix or uterus.
62Perineal Haematoma Infraelevator sopraelevator If < 5 cm Ice packingPressureAnalgesicsIf > 5 cm expandingIncision & drainagesopraelevatorConservative with transfusionsEvacuation of clots and packing for 24 hrsEmbolising the bleeding vessel
63Anal FissureAnal fissure is an ulcer in the squamous epithelium of the anus located just distal to the mucocutaneous junction;In a prospective study before and after deliveryof 163 consecutive women (84 primiparous),Abramowitz et al.37 reported anal fi ssures in 15%during the fi rst 2 months postpartum.
64Caesarean section did not appear to be protective against Anal FissureRisk factorsdyschezia (painful defaecation),heavier babies,long second stage of labour,Anal incontinence after delivery,primiparity,forceps deliveriesperineal damageCaesarean section did not appear to be protective againstanal fissure
65Anal Fissure Pain sorness during defecations Visual examination of anal margineSmall ulcer at the level of mucocutaneous junctionTreatmentRelief of constipationdietfibersit bathsstool softenersMedicaltherapylocal analgesicsGTNBotulinium toxin
66Management of Anal Fissure pregnancy and postpartum Anal fissures in postpartum are associated with low pressure resting tone
67Haemorrhoids Risk factors straining at defaecation constipation, vascular enlargement due to increased intra-abdominal pressureerect postureheredity
68Haemorrhoids Effect of Pregnancy high levels of circulatingprogesteronemechanical obstruction bythe gravid uterusSmooth muscle inhibitionConstipation
69Increased blood volume by 25–40% Haemorrhoids Effect of PregnancyIncreased blood volume by 25–40%Venous engorgement and dilatation
70Haemorrhoids Risk factors include heavier baby long second stage of labourvaginal deliveryinstrumental delivery
71In an observational study of 11,701 women, MacArthur et al.2 found that 8% reported haemorrhoidsof more than 6 weeks’ duration for the fi rsttime within 3 months of birth and an additional10% reported these as ongoing or recurrent symptoms.Two thirds reported the presence of haemorrhoids1–9 years after delivery. Glazener et al.1found that 17% of postnatal women reportedhaemorrhoids (new and recurrent) when questionedin hospital, 22% between delivery and 8weeks postpartum and 15% after 2 months.
72intermittent bleeding (most common symptom) burning sensationitchingIntermittent bleeding of the anusvarying degrees of leakage of mucus, faeces or flatussensation of fullness or a lumpperianal hygienic problemsdiscomfort and/or painCompromission of the quality of lifeaffecting the activities of everyday lifewalkingsitting downemptying bowelssleepingcaring for the family or a new babyAssessment includeanoscopydigital examination
73Treatment Haemorrhoids during pregnancy Often symptoms will resolve spontaneously after birth, and so any corrective treatment is usually deferred to some time after birth.relief of symptoms, especially pain controlComplications of haemorrhoidsacute thrombosisincarceration of prolapsed internal haemorrhoidAggressive treatment such as closed excisional haemorrhoidectomy under local anaesthetic.
74Treatment Haemorrhoids during pregnancy Conservative Managementdietary modificationshigh fibre intake, high liquid intake, stool softenersstimulants or depressants of the bowel transitlocal treatmentssitz baths, creams, ointments or suppositories containing anaesthetics, antiinflammatory drugs, steroids, etc., alone or incombinationdrugs of the flavonoid family such as rutosides that cause decreased capillary fragility
75Treatment Haemorrhoids during pregnancy Alternative Management in severe and non-responsive casesambulatory interventions that usually do not need anaesthetics, such as:injection sclerotherapy,rubber-band ligationcryotherapy,infrared photocoagulation,laser therapyInjection sclerotherapy has been used effectively during pregnancy.86% of antenatal patients (24 of 28) became asymptomatic by means of injection of 5% phenol in almond oil.
76Treatment Haemorrhoids during pregnancy excision surgerystapled anopexyno known trials that have specifically evaluated treatments for severe haemorrhoids during pregnancy and the postpartumperiod.
77Interventions to Prevent Obstetrical Perineal Trauma Planned Caesarean vs. Planned Vaginal BirthExercise in PregnancyAntenatal Pelvic MassagePosition during Labor and BirthEpidural vs. Narcotics Pain ReliefEarly vs. Delayed PushingSecond stage pushing adviceSpontaneous vs. Forceps birthWater Birth
78Routine Episiotomy to Prevent a Tear What Type of Episiotomy is SafestVacuum vs. ForcepsPerinealSupport: Hand on vs. Hand poised
7985% of women who have a vaginal birth will sustain some form of perineal trauma and up to 69% of these will require stitches.Spontaneous or surgicalMcCandlish R et al, Br J Obstet Gynaecol 1998;1. First degree, superficial– skin and subcutaneous tissue of the anterior or posterior perineum– vaginal mucosa– combination of the above resulting in multiple superficial lacerations2. Second degree, deeper– superficial perineal muscles (bulbospongiosus, transverse perineal)– perineal body.Suture or not sutureNot suture: less trauma next delivery, less pain and infection, the wound heals fasterunacceptable aesthetics, sexual function, pelvic floor muscle strength incontinence and prolapse
80four European and one UK RCTs (n = 1,864 primiparous and multiparous women) continuous subcuticular technique of perineal skin closure, when compared to interrupted transcutaneous stitches, was associated with less perineal painKettle C et al, The Cochrane Library, Issue 3. Oxford: Update Software, 2003.Suture materiawound closure, control bleeding, minimise the risk of infection and expedite healing, minimal tissue reaction and be absorbed once the woundhas healed
81The first mention of the surgical management of severe perineal injury appears in Avicenna’sfamous Arabic book, Al Kanoun. He recommendeda form of a crossed or bootlace suture for therepairs of perineal injuries.However, success rates with primary wound unionof perineal wounds reported in the late 1800s werein the region of 50–60%.However, in 1999, Sultan et al, described the overlap technique of primary repair of the EAS (described by Parks previously for secondary sphincter repair).In addition, Sultan et al, highlighted the importance of separate repair of the freshly torn internal anal sphincter (IAS), responsible for maintaining the resting tone of the anal sphincter.Damage to the IAS is associated with incontinence to gas and passive soiling
82The prevalence of third and fourth degree tears, collectively referred to as obstetric anal sphincter injuries (OASIS), appears to be dependent upon the type of episiotomy practised. In centres where mediolateral episiotomies are practised, the rate of OASIS is 1.7% (2.9% in primiparae)9 compared to 12%10 (19% in primiparae)11 in centres practising midline episiotomy.
83End-to-end repairThirty-five studies over a 20 yr with follow-up ranging from 1 to 30 mons:Gas incontinence ranges between 15–61% (n = 35; mean = 39%)Faecal incontinence ranges between 2–29% (n = 25; mean = 14%)
85Thirty-five studies over a 20 yr with follow-up ranging from 1 to 30 mons: following end-to-end repairGas incontinence ranges between 15–61% (n = 35; mean = 39%)Faecal incontinence ranges between 2–29% (n = 25; mean = 14%)
87overlap techniqueMetanalysis of 21 studies , with good results ranging from 74% to 100%Jorge and Wexner et al, Dis Colon Rectum, 199355 patients with faecal incontinence good clinical outcome in 80% at 15 months.Engel et al. Br J Surg 1994Sultan et al, compared to matched historical controls who had an end-to-end repair, anal incontinence could be reduced from 41% to 8% using the overlap technique and separate repair of the internal sphincterBr J Obstet Gynaecol 1999;106:318–23.Malouf AJ et al.Long-term results of overlapping anterior anal-sphincter repair for obstetric trauma.Lancet 2000;355(9200):260–5.
8831 consecutive women who sustained OASIS (3b and fourth degree). Kairaluoma et al. Dis Colon Rectum 2004,31 consecutive women who sustained OASIS (3b and fourth degree).All had an EAS overlap repair immediately after delivery performed by two colorectal surgeons. In addition to end-to-end repair of the IAS, they also performed a levatorplasty to approximate the levators in the midline with two sutures. At a median follow-up of 2 years, 23% complained of anal incontinence, 23% developed wound infection, 27% complained of dyspareunia and one developed a rectovaginal fi stula. Levatorplastytherefore should be avoided during primary anal sphincter repair.
89Poen et al.29 identifi ed 43 women (out of original cohort of 117) who had subsequent vaginal deliveriesfollowing previous OASIS. The rate of analincontinence was 56% compared to 34% in thosewho did not subsequently deliver (relative risk1.6; 95% confi dence interval 1.1–Sangalli et al.14 studied 177 women some 13years after OASIS (48 fourth degree tears). Analincontinence was signifi cantly more common inwomen who had sustained fourth degree tearscompared with those with third degree tears (25vs 11.5%; P = 0.049). Unlike women with previousfourth degree tears, those who had sustained aprevious third degree tear did not demonstrate anincrease in anal incontinence symptoms after asubsequent vaginal delivery.This is in keepingwith the fi ndings of Fenner et al.,25 who found thatthe symptom of worse bowel control was 10 timeshigher in women who sustained fourth as opposedto third degree tears. This could be attributed topersistent injury of the IAS.
90Incontinence when stoma When there is a cloacal injury. Some injuries are so extensive that the anterior half of the anus and the lower third of the vagina are one common cavity.2. When there is an associated rectovaginal fistula. Fistulas to the vagina can be extremely hard to treat;3. In the presence of Crohn’s disease or prior radiation therapy.