Posted in Ultrasound

Reproductive Aspects of Acute Appendicitis

Posted by Professor Mike O’Connor AM on 26 July 2018
Reproductive Aspects of Acute Appendicitis

Introduction

Appendicitis most often occurs between the ages of 10 19 years, with an incidence of between 19-28 per 10,000 before the age of 14 years. Less than 7 per 10,000 children present with appendicitis before the age of 4 years & less than 5% of presentations with appendicitis occur before the age of 5 years. 

Causation 

In tropical climates the cause is often a parasitic worm (pinworm or roundworm) causing obstruction whereas in temperate climates the cause of obstruction of the appendix is more likely to be mechanical twisting or lymphoid hyperplasia associated with viruses such as adenovirus and rubeola or an endoluminal faecolith or undigested food. Periumbilical pain signifies appendiceal colic associated with the obstruction.

As part of the obstruction the lumen of the appendix increases in diameter and this is the basis of the ultrasonic diagnosis of appendicitis: the diameter exceeds 6 mm.

The proliferation of bacteria results in penetration of the wall of the appendix which becomes inflamed and gangrenous. When the pain moves to the right iliac fossa and becomes constant then inflammation of the appendix is underway. Perforation occurs rarely in the first 12 hours of symptoms but is more likely with time thereafter, becoming common after 72 hours. 

Generalized peritonitis develops if the infection is not contained by bowel loops and omentum.

Delays in Diagnosis in Young Girls

Prior to rupture there appears to be no effect of appendicitis on tubal function however when the diagnosis is delayed and perforation has already occurred at the time of surgery tubal damage is increased (Relative Risk =4.8;95% CI =1.5-
14.9).

Future Risk of Ectopic Pregnancy

There appears to be a significantly increased risk of ectopic pregnancy in women who have appendicitis. In one study Elraiyah et al found the risk to be (OR=1.78,95% CI=1.46-2.16). A study by Fernandez et al found a similar increase in the risk of ectopic (RR= 2.2 ;95 percent CI: 1.5-3.2 ) but there appeared to be no difference in the ectopic rate between ruptured and unruptured appendices.

Appendicitis in Pregnancy

In a classic case of appendicitis in pregnancy Tthe pain is periumbilical & colicky initially and then migrates to the right lower quadrant as a constant pain as the inflammatory process progresses Anorexia, nausea and vomiting, if present, follow the onset of pain. Fever up to 38.3ºC and leukocytosis develop later. Many patients have a nonclassical presentation, with symptoms such as heartburn, bowel irregularity, flatulence, malaise, or diarrhea. If the appendix is retrocecal, patients often complain of a dull ache in the right lower quadrant rather than localized tenderness. Rectal or vaginal examination in such patients is more likely to elicit pain than abdominal examination. A pelvic appendix can cause tenderness below McBurney's point. The most common symptom of appendicitis, ie, right lower quadrant pain, occurs close to McBurney's point in the majority of pregnant women, regardless of the stage of pregnancy however, the location of the appendix migrates a few centimeters cephalad with the enlarging uterus, so in the third trimester, pain may localize to the mid or even the upper right side of the abdomen (see figures)

   

Investigations

  1. WCC. Approximately 80 percent of nonpregnant patients with appendicitis have a preoperative leukocytosis (white cells >10,000 cells/microL) and a left shift in the differential. However, mild leukocytosis can be a normal finding in pregnant women: the total leukocyte count may be as high as 16,900 cell/microL in the third trimester.
  2. Ultrasound of Appendix. The initial modality of choice for diagnostic imaging of the appendix in pregnancy is graded compression ultrasonography. The clinical diagnosis of suspected appendicitis is supported by identification of a non-compressible blind-ended tubular structure in the right lower quadrant with a maximal diameter greater than 6 mm.
  3. MRI .For pregnant women whose ultrasound examination is inconclusive for appendicitis, magnetic resonance imaging (MRI) is the preferred next test as it avoids the ionizing radiation of computed tomography and appears to be cost-effective

Obstetric Consequences of Acute Appendicitis in Pregnancy

The main complication is threatened preterm labour. In one study contractions occurred in 83% of all appendicitis patients in pregnancy >24 weeks with 13% exhibiting changes in cervical dilatation. The advent of laparoscopic appendicectomy has encouraged earlier diagnosis and treatment. Delayed diagnosis can have dire adverse effects on the fetus due to prolonged sepsis.

Further Reading

  1. Mueller BA et al.Appendicectomy and the risk of tubal infertility. NEJM 1986.315:1506-1508
  2. Elraiyah T et al. The effect of appendectomy in future tubal infertility and ectopic pregnancy: a systematic review and meta-analysis. J Surg Res 2014.192(2)368-374
  3. Fernandez et al. Appendectomy, a risk factor for ectopic pregnancy La Presse Medicale 1992 21(39):1859-1861.
  4. Williams R, Shaw J Ultrasound scanning in the diagnosis of acute appendicitis in pregnancy. Emerg Med J. 2007 May;24(5):359-60
Posted in: Obstetrcis Ultrasound Other  

NIPT screening & Nuchal Translucency - Complimentary rather than alternatives

Posted by Professor Mike O’Connor AM on 2 May 2018

The advent of the Non Invasive Prenatal Test has been a major advance for the detection of Trisomy 21 (Down s.), Trisomy 18 (Edwards s.) & Trisomy 13 (Patau s.) and reduces the need for invasive tests which have up to a 3% risk of miscarriage.

There has been a subsequent tendency to abandon the previous nuchal translucency ultrasound and biochemical test because of the increased accuracy of detection of the trisomies with the NIPT test which can detect 99% of Down syndrome fetuses c.f. a 90% detection rate with NT Plus.

What seems to be less well appreciated is that the NIPT does not provide a full karyotype as it relies on frag-ments of fetal DNA within maternal blood .These are then used to detect T211,T18 or T13 using specific probes. More recently a further probe is availa-ble to detect 22 q deletions as found in DiGeorge syndrome: a complex syndrome involving cardiac ,facial, skeletal and neurological abnormalities which has an incidence of 1/1000.

Reliance on an NIPT to exclude a fetal aneuploidy is unsound and a positive NIPT will still require confirmation using genetic amniocentesis or CVS. The value of a nuchal translucency test between 11-13 weeks is that it will give additional information not available with an NIPT test.

For example, the nuchal translucency is not just increased (>3 mm) in fetal aneuploidies such as Down syndrome and Turner's syndrome (45 XO) but is also increased in fetal cardiac malformations: more than 55% of all major congenital heart defects in one series (Hyett et al 1999) had an NT > 95 per-centile (NR 1.8-2.35 mm) and the negative predictive value of a normal NT was 99.9%.

Furthermore a careful ultrasound scan at 11-13 weeks can give additional information such as cervical length ( values <3 cm can predict cer-vical incompetence) as well as basic information such as cranial anatomy (eg excluding anencephaly), spine, stomach, kidneys, bladder & presence of all 4 limbs. These non-cardiac features can be reasonably assessed in between 75-98% of cases between 11-14 weeks. Other important ultrasound findings at 11-13 weeks include detection of uterine fibroids and ovarian tumours which may cause complications such as red degeneration and torsion respectively later in pregnancy.

Fetal morphology scans: diagnostic value and limitations especially fetal heart anomalies

The fetal morphology scan is normally performed between 18-20 weeks gestation. If performed by skilled ultrasonologists it will detect a significant number of serious fetal anomalies. It is important to remember that only about one third of structural abnormalities are associated with an abnormal karyotype. The basic information available includes:

  1. An assessment of gestational age (+/- 7-10 days error)
  2. An assessment of fetal morphology
  3. An assessment of placental localization (bearing in mind that the vast majority of 'low lying' placentae will not remain so by term)

Approximately 1% of liveborn fetuses have congenital heart disease (CHD). What is concerning is the failure to diagnose a large number of these fetuses with (CHD) at that gestational age. A little later at 22 weeks there is a better yield of diagnoses of CHD.

The 1993 RADIUS study surveyed 92 obstetric practices and 17 family practices in 6 US States and identified 15,530 low risk pregnant women who were scanned between 15-22 weeks and 31-35 weeks by 28 ultrasound referral laboratories staffed by 91 qualified sonologists. Of those women (whose fetal anomaly rate was 2.3%) only one third had one (or more) major fetal anomalies detected by 24 weeks. It demonstrated that few of the CHD's were detected .No improvement in overall perinatal outcome could be demonstrated. 

More recently one US study (Pinto et al, 2011) over a 10 year period found that only only 39% of 1474 cases of significant CHD were detected, with no improvement in detection rate over the 10year period. Detailed fetal echocardiography can improve the detection rate but this is impractical for large populations. The 4 chamber cardiac scan is the basic standard and this will miss defects such as transposition of the great arteries (TGA), tetralogy of Fallot (TOF), double-outlet right ventricle (DORV) and truncus arteriosus. The 4 chamber view cardiac view is likely to identify complete atrioventricular septal defect (AVSD), congenitally corrected transposition of the great arteries (CCTGA), tricuspid valve disease (including Ebstein's anomaly) and all single ventricle defects including hypoplastic left heart syndrome (HLHS). A circumspect approach is therefore required when receiving a normal fetal morphology scan result.

Further reading:

  • Alldred SK et al. First trimester ultrasound tests alone or in combination with first trimester serum tests for Down's syndrome screening.Cochrane Database Syst Rev. 2017 Mar 15;3:CD012600. doi: 10.1002/14651858.CD012600.
  • Sharifzadeh M et al. Normal reference range of fetal nuchal translucency thickness in pregnant women in the first trimester, one center study J Res Med Sci. 2015 Oct; 20(10): 969973.
  • Hyett J,Perdu M,Sharland G, Snijders R,Nicolaides K. Using fetal nuchal translucency to screen for major congenital cardiac defects at 10-14 weeks of gestation: population based cohort study BMJ. 1999 Jan 9; 318(7176): 8185.
  • Pinto NM et al. Barriers to prenatal detection of congenital heart disease: a populationbased study Ultrasound Obstet Gynecol. 2012 Oct;40(4):418-25. doi: 10.1002/uog.10116. Epub 2012 Sep 17.
  • Ewigman BG et al. Effect of prenatal ultrasound screening on perinatal outcome. RADIUS Study Group.N Engl J Med. 1993 Sep 16;329(12):821-7.
Posted in: Obstetrcis Ultrasound Miscarriage  

Reaccreditation for Diagnostic Ultrasound

Posted by Dr Mike O'Connor on 7 October 2015

In September 2015 this practice was reaccredited for diagnostic ultrasound services under the stringent Commonwealth Health Standards.  We want to tell our patients that their well-being is our priority. QIP accreditation assures patients that we are committed to providing ultrasound care which meets the Standards laid down by the Commonwealth Department of Health and Ageing.

Dr O'Connor offers a range of diagnostic ultrasound services including early and late obstetric imaging, gynaecological scans and urological imaging.

Reaccreditation of our ultrasound service has now been approved until 31 January 2020 when we will again undergo accreditation.
 

Posted in: Ultrasound  

Potential Fetal Anomalies

Posted by Dr Mike O'Connor on 3 March 2013

Potential Fetal Anomalies missed at the 19 week ultrasound

Fetal anomaly scans at about 19 weeks of gestation are often thought by patients to exclude all major fetal anomalies. However this is not the case: for example it has been noted that up to 50% of congenital heart malformations are missed (RADIUS Study) in this way. Another example of this was a Dutch study of over 5,000 patients scanned between 16 and 24 weeks. Those skilled sonologists and sonographers   missed 10 major and 42 minor congenital heart malformations on the basis of a normal 4 chamber view of the fetal heart. Only 7 fetuses had an abnormal 4 chamber view and of those only 2 had congenital heart disease.

Hydrocephaly often does not become apparent until 16 to 18 postmenstrual weeks or later. If one were to rely on a morphology scan to identify Down syndrome then 50% would be missed.
Specific serious anomalies which may be missed include:

  • Hypo-plastic left heart syndrome
  • neuronal migration disorders such as cortical dysplasia: a cause of intractable epilepsy
  • hydrocephaly caused by such problems as aqueduct stenosis, Dandy Walker syndrome, absent corpus callosum

Some interest is focussed presently on the demonstration of intracranial translucency (which is found parallel with nuchal translucency). Its absence may suggest open spina bifida because of commonly associated changes in the fourth ventricle (Arnold Chiari malformation)

Posted in: Ultrasound  

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