Abnormalities Of The Passage-williams

Abnormalities of the Passage Liu Yuling M.D. Department Of Obstetrics & Gynecology Renmin Hospital Wuhan University

Abnormalities of the Passage  Constitute pelvic dystocia

That is aberrations of pelvic architecture and its relationship to the presenting part.  Be related to 

  

Size or configurational alterations of the bony pelvis Soft tissue abnormalities of the birth canal Reproductive tract masses or neoplasia Aberrant placental location

Abnormalities of the Passage  Pelvic Types  Pelvimetry  Pelvic Contractions  Soft-Tissue Dystocia

Bony pelvis component

innominate bone (L,R)

 Sacrum  Coccyx

ilium (L,R) ischium (L,R) pubis (L,R)

(L,R)coccyx, and The pelvis is composed of four bones: pubis the sacrum, two innominate bones. Each innominate bone is formed by the fusion of the ilium, ischium, and pubis. The innominate bones are joined to the sacrum at the sacroiliac synchondroses and to one

Pelvis anatomical marks  Sacral promontory

 Ischial spine (L,R)

 Symphysis pubis

The sacral promontory and symphysis pubis are important for vaginal examination to determine the true conjugate diameter The ischial spines are of great obstetrical importance because the distance between them represents the shortest diameter of the pelvic cavity They also serve as valuable landmarks in assessing the level to which the presenting part of the fetus has descended into the true pelvis

PELVIC PLANES The pelvis is described as having four imaginary planes: Inlet plane Greatest plane Midplane (Least plane) Outlet plane

Vertical chart of pelvic four planes

4

1: Inlet plane the superior strait 2: the greatest plane of no obstetrical significance 3: The plane of the midpelvis the least plane 4: Outlet plane the inferior strait

Important pelvic planes internal parameters Inlet plane ------11 cm true conjugate diameter

Midplane -------10 cm interspinous diameter

Outlet plane --- 9 cm bituberous diameter

Important pelvic planes internal parameters Inlet plane ------11 cm true conjugate diameter The obstetrically anteroposterior diameter is the shortest distance between the promontory of the sacrum and the symphysis pubis

Important pelvic planes internal parameters

Midplane -------10 cm interspinous diameter

Important pelvic planes internal parameters

Outlet plane --- 9 cm bituberous diameter

Summary Bony Pelvis : sacrum, ilium, innominate bone 3 marks: sacrum promontory, iliac spine, symphysis pubis 4 planes: inlet-11, greatest, least-10, outlet-9 cm

Pelvic dystocia, particularly that is due to small bony architecture, is the most common cause of passage abnormalities The etiology and diagnosis of pelvic abnormalities begins with the shape, classification, and clinical assessment of the adult female pelvis

Pelvic Types 

Using roentgenographic studies, Caldwell and Maloy classified the 4 major types of adult pelvis    



Gynecoid pelvis Android pelvis Anthropoid pelvis Platypelloid pelvis

Pure forms of the pelvic types are rare; mixed elements are more often present in each type of pelvis

36.6%

Flat(platypelloid) 47.3%

gynecoid

10.9%

anthropoid 5.8%

android

Gynecoid The most typically “female” type

•Shape of inlet ； Oval configuration •Transverse diameter is slightly greater than the anteroposterior •Side walls are straight •Ischial spines are not prominent •Sacrum is concave •Subpubic angle is wide

•Seem suited for delivery of most fetuses

•Incidence in white women is 50%

android

•Shape of inlet: Wedge-shaped •Side walls are convergent •Ischial spines are prominent •Sacrum is inclined anteriorly in its lower third •Incidence is 33% in white women and 15% in black women •Be associated with persistent occiput posterior position and deep transverse arrest dystocia

platypelloid

•A rare type (incidence is less than 3% in white women) •Transverse diameter is wide with respect to the antero – posterior diameter •Deep transverse arrest pattern of labor are more commonly associated with this pelvic type

anthropoid

•The antero-posterior diameter is greater than the transverse diameter •Side walls are divergent •Sacrum is inclined posteriorly •Be most often associated with persistent occiput posterior dystocia

Pelvimetry 

In some unusual cases, pelvimetry is often helpful in predicting the prognosis     



 

traumatic pelvic fractures rachitic pelvis chondrodystrophic dwarf pelvis Kyphotic and scoliotic pelvis exostoses （ Benign hypertrophy that projects outward from the surface of bone, often containing a cartilaginous component ） bony neoplasms

X-ray pelvimetry Clinical pelvimetry

X-ray pelvimetry  



Have been the most widely used pelvimetric method Has fallen into limited use that radiation exposure subjects the fetus to an increased risk of oncogenesis Be useful in a few elected instances  

vaginal breech delivery gross bony distortion  



previous pelvic fracture rachitic deformity

Both ultrasonography and magnetic resonance imaging have been used to investigate pelvic size and shape for evidence of pelvic contraction obstructing the normal progress of labor

X-ray pelvimetry



Three techniques of x-ray pelvimetry are in general use Colcher-Sussman system  

 

Be most widely used Compares the anteroposterior and transverse diameters of a given pelvis with the average and lower limit of normal values

Mengert’s method Ball method

Clinical pelvimetry  Has largely supplanted x-ray pelvimetry

in the routine evaluation of most obstetric patients  Estimation of the diagonal conjugate has been particularly helpful  The diagnosis of fetopelvic disproportion has generally become a diagnosis of exclusion

Parameters of the pelvic inlet

conjugate diameter 11cm transverse diameter 13cm oblique diameters 12.75cm

Three anteroposterior diameters of the pelvic inlet

12.5-13cm

diagonal conjugate, DC

Pelvic Inlet Measurements The diagonal conjugate is clinically estimated by measuring the distance from the sacral promontory to the lower margin of the symphysis pubis . The distance between the mark and the tip of the second finger is the diagonal conjugate.  The obstetrical conjugate is computed by subtracting 1.5 to 2.0 cm, depending on the height and inclination of the symphysis pubis. If the diagonal conjugate is greater than 11.5 cm, it is justifiable to assume that the pelvic inlet is of adequate size

Parameters of obstetric midpelvis anteroposterior diamete

[*1]

transverse diameter

10cm

坐骨棘间径 interspinous diameter (biischial diameter) Midpelvis Estimation Clinical estimation of midpelvic capacity by any direct form of measurement is not possible. If the ischial spines are quite prominent, the sidewalls are felt to converge, and the concavity of the sacrum is very shallow, then suspicion of a contraction is aroused.

The pelvic outlet

2 triangles: anterior triangle posterior triangle Base of both: intertuberous diameter

1. transverse diameter 9cm 2. Anterior sagittal diameter 6cm 3. Posterior sagittal Diameter 8.5cm

Pelvic Outlet Measurements •The measurement of the 8.5-9cm transverse diameter of the outlet can be estimated by placing a closed fist against the perineum between the ischial tuberosities. •Usually the closed fist is wider than 8 cm. • A measurement of more than 8 transverse outlet, TO cm is considered normal.

90 度 Angle of pubic arch

Pelvic Contractions  Inlet contraction  Midpelvic-outlet contraction

 Pelves with abnormality of shape and bo

Inlet contraction

Definition  The anteroposterior

diameter is less than 10 cm  The transverse diameter is under 12 cm  Or both

Manifestation  A floating vertex presentation with no

descent during labor  An abnormal presentation  A prolapsed cord, prolapsed extremity or both  Poor progress in labor and uterine dystocia

Manifestation Considerable molding of the fetal head  Caput succedaneum formation  Prolonged rupture of the membranes  Pathologic retraction ring 

uterine rupture

Pathological retraction ring

Diagnosis  Inlet contraction may be detected clinically

by   

X-ray pelvimetry Clinical estimation of the diagonal conjugate Inability to perform the Müller-Hillis maneuver

Manually pushing the fetal head into the pelvis with gentle fundal pressure

Estimation of fetal head size 

Clinical estimation - Muller method  In

an occiput presentation, the brow and the suboccipital region are grasped through the abdominal wall with the fingers and firm pressure is directed downward in the axis of the inlet.  Fundal pressure by an assistant usually is helpful.  The effect of the forces on the descent of the head can be evaluated by concomitant vaginal examination.

The Müller-Hillis maneuver

No disproportion The head readily enters the pelvis, and vaginal delivery can be predicted.

No disproportion maybe Inability to push the head into the pelvis does not necessarily indicate that vaginal delivery is impossible

fetaopelvic disproportion Flexed fetal head that overrides the synphysis pubis → presumptive evidence of disproportion

Treatment  Neglected cases of inlet contraction are rare

and prognosis is excellent  

Compare the patient’s progress with known labor curves Suspect possible inlet contraction on the basis of clinical examination

 With continuous fetal monitoring in these cases,

fetal well – being may be ensure, even with concurrent use of dilute oxytocin  Cesarean section is the treatment of choice in true inlet contraction

Midpelvic-outlet contraction

Parameters of obstetric midpelvis anteroposterior diamete

[*1]

transverse diameter

The pelvic outlet

2 triangles: anterior triangle posterior triangle Base of both: intertuberous diameter

1. transverse diameter 9cm 2. Anterior sagittal diameter 6cm 3. Posterior sagittal Diameter 8.5cm

Midpelvic-outlet contraction

The midpelvis The pelvic outlet

Anterior transverse diameter sagittal diameter (cm) (cm)

Posterior sagittal Diameter (cm)

Sum of transverse diameter and Posterior sagittal diameter(cm)

<11.5

<5

<13.5

<9.5 (Interspinous diameter) <8 (intertuberous diameter)

<15

Transverse diameter 8.5-9cm

Sum = transverse diameter + Posterior sagittal diameter(cm) Sum >15cm

Sum <15cm

Manifestation 1  a prolonged second stage  persistent occiput posterior position

deep transverse arrest  Molding of the fetal head caput succedaneum formation

Manifestation 2  Uterine rupture  pressure necrosis of the surrounding

tissues of the birth canal by the fetal head  

Vesicovaginal fistula rectovaginal fistula

Prognosis Poor prognosis is typical in midpelvic – outlet contraction  Due to difficult midforceps rotation  Duo to difficult vaginal delivery

Treatment  Cesarean section is therefore the delivery

method of choice in this complication

Pelvic contraction Anteropost Transverse erior diameter diameter (cm) (cm) Inlet

< 10

Posterior sagittal Diameter (cm)

Sum of transverse diameter and Posterior sagittal diameter(cm)

<5

<13.5

< 12

The midpelvis

<9.5 (Interspinous diameter)

The pelvic outlet

<8 (intertuberous diameter)

<15

Soft-Tissue Dystocia  Congenital anomalies  Scarring of the birth canal  Pelvic masses  Low-lying placenta

Congenital anomalies 

Bicornuate uterus 

Generally causes malpresentation

Congenital anomalies Longitudinal and transverse vaginal septa  

A longitudinal septum is usually pushed aside or spontaneously lacerated during labor Transverse septa may require incision to permit vaginal delivery

Imperforate transverse vaginal septa

Transverse Vaginal Septum

Congenital anomalies 

Conglutination of the external cervical os  

 

Is of uncertain etiology may be either congenital or acquired following previous injury Is manifested as a small external os that fails to dilate after full effacement Mechanical dilatation is usually required and os often easily accomplished with just the examining digit

Scarring of the birth canal Previous scarring from injury to the birth canal may cause tissue rigidity and dystocia  Previous birth laceration  Conization  Cauterization, rape injury in a small child  Caustic abortifacient injury to the vaginal vault and cervix

Management  Episiotomy

repair of extensive laceration  Cesarean section occasionally be required to treat these rare occurrences

Pelvic masses  Carcinoma of the cervix  Leiomyomas of the cervix or

lower-uterine segment  Distended bladder  Ovarian neoplasm  A transplanted pelvic kidney Management Cesarean section and removal of the neoplasm may be required.

Low-lying placenta  A marginal or low-lying placenta may prevent

normal fetal descent in labor.

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