Week 3 Flashcards
What kind of nerve fibres supply the structures in the pelvis?
Sympathetic
Parasympathetic
Visceral afferent
What kind of nerve fibres supply the structures in the perineum?
Somatic motor
Somatic sensory
Regarding reproductive system motor function, which of the following nerve types are involved in the following…
- uterine “cramping”
- uterine contraction
- pelvic floor muscle contraction (e.g. during sneezing)
Uterine cramping - hormonal (sympathetic/parasympathetic)
Uterine contraction - hormonal (sympathetic/parasympathetic)
Pelvic floor muscle contraction - somatic motor
Regarding reproductive system pain, which nerve types are involved in the following…
- pain from the adnexae (ovaries and fallopian tubes)
- pain from the uterus
- pain from the vagina
- pain from the perineum
Pain from the adnexae - visceral afferents
Pain from the uterus - visceral afferents
Pain from the vagina - visceral afferents (pelvic part)/somatic sensory (perineum)
Pain from the perineum - somatic sensory
Describe the nerve fibres involved in pain sensation of the superior aspects of pelvic organs/touching the peritoneum
How is pain perceived by the patient?
Visceral afferents that run alongside sympathetic fibres
Enter the spinal cord between T11-L2
Pain is perceived by the patient as being suprapubic
Describe the nerve fibres involved in pain sensation of the inferior aspects of pelvic organs/not touching the peritoneum
How is pain perceived by the patient?
Visceral afferents run alongside parasympathetic fibres
Enter the spinal cord at S2, S3, S4
Pain is perceived by the patient in the S2,3,4 dermatome (perineum)
How does nerve innervation for pain sensation change for structures that pass through the levator ani i.e. from pelvis to perineum (urethra, vagina etc.)
Above levator ani
- visceral afferents
- parasympathetic fibres
- spinal cord levels S2, S3, S4
Below levator ani
- somatic sensory
- pudendal nerve
- spinal cord levels S2, S3, S4
- localised pain within the perineum
Which nerve roots are affected by a spinal nerve block?
What kind of anaesthesia is delivered?
Will patients feel contractions?
T11-L2 is blocked
Anaesthesia from the waist down - intra- and subperitoneal plus somatic areas affected
Patients will NOT feel contractions
Which nerve roots are affected by a caudal/epidural block?
What kind of anaesthesia is delivered?
Will patients feel contractions?
S2, S3, S4
Anaesthetises subperitoneal plus somatic areas innervated by the pudendal nerve (basically everything south of the pelvic pain line)
Patients WILL feel contractions
Which nerve roots are affected by a pudendal nerve block?
What kind of anaesthesia is delivered?
Will patients feel contractions?
No nerve roots affected, local block of the pudendal nerve
Only anaesthetises areas innervated by the pudendal nerve
Patients WILL feel contractions
What vertebral level does the spinal cord become the cauda equina?
What vertebral level is anaesthetic injected into when performing a spinal or epidural?
Spinal cord becomes the cauda equina at L2
Anaesthetic is injected at L3/L4 (or L4/L5)
What layers does the needle need to pass through when performing a spinal anaesthetic?
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space (contains fat and veins)
Dura mater
Arachnoid mater
What should you get a patient to do initially after you’ve given them a spinal anaesthetic?
Why?
Keep patient sitting initially as they may get headaches if they lack back
This is due to the anaesthetic fluid being added to the CSF, which increases the ICP. This also happens when taking a LP
What layers does the needle need to pass through when performing an epidural anaesthetic?
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Epidural space (containing fat and veins)
Then stops before penetrating the dura mater
How do sympathetic nerves exit the spinal cord?
Exit with the T1-L2 spinal nerves
Then travel to sympathetic chains that run the length of the vertebral column
Then pass into all spinal nerves (anterior and posterior rami/named nerves)
What type of nerve fibre do all spinal nerves and their named nerves contain?
What do these nerve types supply?
As a result, what does a blockade of these nerves cause when performing a spinal anaesthetic?
All spinal nerves and their named nerves contain sympathetic fibres (including femoral, sciatic, obturator, pudendal)
These sympathetic fibres supply all arterioles with sympathetic tone
Blockade would therefore result in loss of sympathetic tone to all arterioles in the lower limb = vasodilation
Presents with flushed looking skin, warm lower limbs, reduced sweating and hypotension - all indicates that the spinal anaesthetic is working
What motor control does the pudendal nerve allow for?
Control of the external anal and external urethral sphincters
What nerve roots does the pudendal nerve arise from?
Branch of the sacral plexus - S2, S3, S4
What procedures might a pudendal nerve block be used for?
Episiotomy incision
Forceps use
Perineal stiching post-delivery
Describe the path of the pudendal nerve from exiting the pelvis to supplying the perineum
Exits pelvis via the greater sciatic foramen
Passes posteriorly to the sacrospinous ligament
Then re-enters the pelvis/perineum via the lesser sciatic foramen
Then travels in the pudendal canal (Alcock’s canal), before branching to supply the structures of the perineum
The pudendal canal is a passageway within what fascia?
What travels within this passageway alongside the pudendal nerve?
Pudendal canal is a passageway within the obturator fascia
Travels with the internal pudendal artery and vein, and nerve to obturator internus
What bony feature can be used as a landmark when performing a pudendal nerve block?
Which other nerve also supplies part of the perineum and may need to be blocked?
The ischial spine can be used as a landmark to administer the pudendal block
The ilioinguinal nerve supplies the anterior part of the perineum and may need to be blocked also
What damage may occur during vaginal delivery and what could this result in?
The pudendal nerve can become stretched, leading to incontinence/loss of sensation
Fibres within the levator ani (puborectalis), or the external anal sphincter muscle can also be torn. This could be 1st degree, 2nd degree or 3rd degree, and could result in a weakened pelvic floor > faecal incontinence
Which direction is the incision for an episiotomy typically done in?
Typically postero-lateral incision into the relatively safe zone of the fat-filled ischioanal fossa - avoids extending into the rectum
What gynaecological indications are there for using radiology?
Diagnosing the cause of pelvic pain
Assessment of pelvic masses
Investigation of abnormal menstrual bleeding
Assessment of patients with post-menopausal bleeding
Investigation of infertility
Interventional radiology e.g. fallopian tube recanalisation, uterine artery embolisation etc.
What are the two main forms of USS used in gynaecology?
What is each used for?
Trans-abdominal USS - used to scan the pelvic organs and for a quick assessment of the upper abdoment (hydronephrosis, ascites etc.)
Trans-vaginal USS - used so that the probe is as close to the pelvic organs as possible. Higher frequency with a shorter wavelength and better spatial resolution, however higher frequencies are more likely to be scattered in the body (hence close proximity required)
Often, both are done at the same attendance
A transabdominal USS requires a full/empty bladder
What are some of the advantages and disadvantages of this technique?
Transabdominal requires full bladder - acts as an acoustic window, uncomfortable
Advantages
- safe
- readily available
- no ionising radiation
Disadvantages
- difficult to obtain good images in obese patients/those with gaseous distension
- operator dependent
- difficult to reproduce exactly the same images
A transvaginal USS requires a full/empty bladder
What are some of the advantages and disadvantages of this technique?
Transvaginal requires an empty bladder
Advantages
- excellent image of the pelvic organs
Disadvantages
- more invasive
- not suitable in people who have not been sexually active
- may not demonstrate the full extent of large pelvic masses (ideally follow with transabdominal)
When is CT scanning used in gynaecology?
Often as a second-line investigation after USS in patients with acute abdo pain
Can also be used to assess post-surgical complications - e.g. small bowel obstruction secondary to adhesions, post-operative collections etc.
Also used to stage gynaecological malignancy especially ovarian and endometrial cancers
Used to assess response to treatment in patients after chemo/radiotherapy
CT scanning - advantages and disadvantages
Advantages
- quick
- entire chest and abdo can be assessed in one scan
- good images generated
Disadvantages
- high radiation dose with a significant amount delivered to the ovaries
- doesn’t provide optimal depiction of different pelvic organs (MR is better at providing good tissue resolution)
MRI - advantages and disasdvantages
Advantages
- no ionising radiation
- excellent depiction of organs
- can give some idea about the composition of soft tissue masses e.g. contain fluid, fat, blood?
- very good for cancer staging, especially cervical
Disadvantages
- time consuming
- poor depiction of lung parenchyma (perform CT if query pulmonary mets)
- claustrophibic patients X
- contraindications - pacemakers, artificial metallic heart valves, nerve stimulators, cochlear implants etc.
What is hydrosalpinx?
Fluid within fallopian tubes
How is endometriosis diagnosed?
Can be difficult, patients may need diagnostic laparoscopy (gold standard)
Altered blood and degradation products within endometriosis deposits produce a characteristic change on MR - returns high signal on T1 (looks white) and returns lower signal sequences on T2 (looks grey)
NB - fat also appears white on T1, so it can be hard to distinguish the two. Fat suppression can be done
When is hysterosalpingography (HSG) performed? How is it done?
Mainly used to assess tubal patency in patients with infertility
Can also be used to assess the outline of the uterine cavity
X-ray screening procedure taking 3-5 mins that involves cannulating the cervix and inserting a radiopaque contrast dye into the uterine cavity
Ovarian cancer disseminates via peritoneal spread
What signs are seen?
Ascites
Omental and peritoneal nodules, as well as subdiaphragmatic dpeosits/liver deposits
Malignant pleural effusions may also be seen
Lymph node mets, lung mets and liver mets are less common and tend to be seen in patients in whom the disease behaviour has been modulated by chemotherapy/cancers with the BRCA1 mutation
What imaging is best used to stage cervical cancer?
MR (especially T2) is far better than CT at depicting local disease
However, CT is often used to determine whether or not there are distant mets
What is the best imaging tool to use when establishing whether or not there is abnormal endometrial thickening i.e. in the case of endometrial cancer?
Transvaginal USS is the best method to establish abnormal thickening in a post-menopausal patient with bleeding
MR can be used to assess the degree of myometrial invasion, but CT is used to look for distant mets (pulmonary and nodal)
From where does alpha-fetoprotein originate?
Produced in the liver of the developing fetus and the yolk sac
What comprises the triad of symptoms seen in pre-eclampsia?
Raised blood pressure
Proteinuria
AKI
What is HELLP Syndrome?
Severe form of pre-eclampsia
Haemolysis
Elevated Liver Enzymes
Low Platelets
Usually occurs antepartum between 27 and 37 weeks’ gestation; 15% to 30% of cases present initially postpartum. Significant diagnostic and therapeutic challenge because only 80% to 85% of affected patients present typically with hypertension and proteinuria.
Should be considered in any pregnant patient presenting in the second half of gestation or immediately postpartum with significant new-onset epigastric/upper abdominal pain until proven otherwise.
Associated with progressive and sometimes rapid maternal and fetal deterioration.
How is HELLP Syndrome managed?
Early aggressive management is required
IV magnesium sulphate (prevents fitting)
IV dexamethasone (encourages production of surfactant)
Control of blood pressure to prevent or minimise severe systolic hypertension (labetolol, hydralazine), replacement of blood products as needed, and timely delivery of the fetus and placenta
How does HELLP syndrome present?
Nausea and vomiting
Hypertension
Brisk tendon reflexes
RUQ/epigastric pain
Headache, malaise, hypertension
Typically obese patients
What is meant by the term ‘Rhesus negative’?
What would you expect to find in the blood of a sensitised mother?
Rh -ve means that a person doesn’t have the Rh(D) antigen
In a sensitised mother, you would expect to find antibodies to the Rh(D) antigen
In an affected Rh(D) +ve baby with a Rh(D) -ve mother, how would you expect the following cord blood parameters to change?
- Haemoglobin
- Bilirubin
- Coombs test (tests for haemolytic anaemia)
Haemoglobin would fall
Bilirubin would rise
Coombs test would be positive showing agglutination
What can be given to a mother to prevent Rhesus isoimmunisation?
When is this given?
How is it given?
Can give Anti-D
Offer at 28 weeks and given again within 72 hours of birth
Given via IM injection into the thigh, arm or glute
Under what circumstances should Anti-D be given to a mother after delivery (3)?
How much is given?
All of the following…
- if the mother is Rh(D) -ve
- if the baby is Rh(D) +ve
- there is no maternal anti-D detectable in the mother’s serum i.e. she hasn’t already been immunised
500IU of IgG anti-D is given intramuscularly within 72 hours of delivery
If giving prophylactically, 250IU is given before 20 weeks gestation and 500IU is given after 20 weeks
When is Rhesus status important in pregnancy?
When the mother is Rh(D) -ve and her baby is Rh(D) +ve, and this is not her first pregnancy
This means that in the initial pregnancy she created anti-Rh(D) antibodies, which will then attack subsequent pregnancies resulting in haemolysis called Haemolytic Disease of the Newborn
How are sensitivity and specificity calculated?
Sensitivity = true positives/(positive + false negative)
Specificity = true negative/(negative + false positive)
At a standard booking examination, what information is taken from the expecting mother (history, examination, investigation)?
History - menstrual, medical, obstetric, family and social
Examination - height, weight, blood pressure, cardiovascular status, abdomen
Investigation - Hb, ABO and Rhesus, Syphilis/HIV/Hep B+C screen, urinalysis, USS
What is Naegele’s Rule and how does it work?
Used to provide an estimated date of delivery
Just add 9 months and 7 days to the date of the last menstrual period to arrive at the due date = 280 days
4% deliver on due date, 60% deliver within 1 week of it and 90% deliver at term
At the follow-up antenatal visit after the initial booking scan, what information is taken from the expecting mother (history, examination, investigation)?
History - physical and mental health, fetal movements
Examination - BP and urinalysis, symphisis-fundal height, lie and presentation, engagement of presenting part, fetal heart auscultation
Investigation - USS for fetal anomalies
What is placenta previa?
How is it managed?
Placenta praevia is when the placenta is low lying in the womb and COVERS all or part of the cervix
In most women, as the womb grows upwards, the placenta moves with it so that it is in a normal position before birth, so just needs to be monitored
If PP is detected on an earlier USS (between 18-21 weeks), another abdominal scan is usually offered at 32 weeks
When screening for Down’s Syndrome using Nuchal Thickness scanning, a value above what would be considered to be abnormal?
What trimester is this performed in?
A value above 3.5mm would be considered abnormal when the crown-rump length is between 45 and 84mm
This is done in the first trimester
When continuing with the Down’s Risk Assessment, what test is done next and what does it measure?
What trimester is this performed in?
In the second trimester, a blood sample is taken at 15-20 weeks
This sample is screened for HCG and AFP. This information, + maternal age and gestation give an indicator of personal risk.
If risk exceeds 1:250 then further testing is done e.g. with amniocentesis
When can amniocentesis be performed? What is the risk of miscarriage?
When can CVS be performed? What is the risk of miscarriage?
Amniocentesis - usually performed after 15 weeks, rate of miscarriage is 1%
CVS - usually performed after 12 weeks, rate of miscarriage 2%
From what point onward is symphysis-fundal height recorded?
From 24 weeks of pregnancy onwards
How does SRY protein cause degeneration of the paramesonephric duct and the generation of dihydrotestosterone?
SRY causes the formation of Sertoli cells, which then secrete AMH (anti-Mullerian hormone), which then causes degeneration of the paramesonephric duct
Sertoli cells also stimulate gonadal ridge cells to from Leydig cells (secrete testosterone). Testosterone then induces the formation of the epididymis, vas deferens and seminal vesicles
Via 5-alpha-reductase, dihydrotestosterone is then formed, which induces male-specific genitalia development and prostate
At what vertebral level do the testes originate?
At what time do they begin to descend, and via what structure?
Failure of this descent may result in what?
Originate at the 10th thoracic level
Pulled caudally by the gubernaculum from week 7
Failure of descent in one or both testes is called cryptorchidism
Is the foetal and maternal blood in direct contact with one another?
No - each villus contains foetal capillaries separated from maternal blood by a thin layer of tissue creating the intervillous space
How does foetal O2-saturated blood return to the foetus?
How does maternal O2-poor blood flow back?
Oxygen-saturated blood returns to the foetus via the umbilical vein
Oxygen-poor blood flows back into the uterine veins
What is the clinical significance of the Bohr effect?
Allows for greater amount of O2 unloading to tissues under higher metabolic demand and subsequent CO2 release which lowers the pH e.g. skeletal muscles being used
This is proportional to the amount of metabolic demand (amount of pCO2 increase). Also enhanced in the generation of lactic acid, which results in a greater amount of H+ ions and thus reduces the pH, causing a further shift to the right of the oxygen dissociation curve
What does a shift to either the left or right mean for affinity for O2 in the oxygen dissociation curve?
What factors cause a shift to the right or left?
Shift to the right results in a lower affinity for O2, meaning more oxygen can be unloaded to tissues. Shift to the left means a higher affinity for O2, and thus oxygen is retained by Hb
Factors causing a shift to the right include…
- decreased pH (/raised H+ ions)
- increased pCO2
- increased temperature
- increased 2,3-DPG (causes a conformational change in Hb making it more likely to release oxygen)
How can hormonal changes induced by the placenta bring about hypertension and gestational diabetes?
Placenta produces corticotropin-releasing hormone (CRH), which then causes a rise in maternal ACTH
Rising ACTH causes aldosterone (increases sodium retention) and cortisol (increases blood sugar through gluconeogenesis, suppresses the immune system and aids in metabolism of fat, proteins and carbohydrates) release
Aldosterone release causes hypertension
Cortisol release causes insulin release and gestational diabetes
How are CO2 levels lowered in the pregnant woman?
Resp rate increases
Tidal and minute volume increases
pCO2 decreases slightly
Importantly - vital capacity and pO2 DO NOT CHANGE
When examining multiple pregnancy with USS, what would the following signs indicate?
- Lambda sign
- T sign
Lamda sign - DIchorionic DIamniotic
T sign - MONOchorionic diamniotic
