Imaging in Twin-to-Twin Transfusion Syndrome

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Twin-to-twin transfusion syndrome (TTTS) occurs in monochorionic (MC) twins and is due to arteriovenous anastomosis in the shared placenta. The donor twin is small and anemic. The recipient twin is polycythemic, large, and at risk for high-output cardiac failure. The mortality rate is 40-90%, with both twins at risk.

Ultrasonography remains the cornerstone test in the diagnosis of twin-to-twin transfusion syndrome (TTTS). ^[1]   Most fetal interventions are currently ultrasonographically guided. Monochorionic (MC) twin gestations are high-risk pregnancies, largely related to the vascular anatomy of the shared placentae and to the presence of intertwin vascular connections. These anastomoses are implicated in TTTS and in co-twin sequelae after the intrauterine death of 1 twin. Obstetric Doppler sonography can be used to assess these high-risk pregnancies and to interrogate the vascular connections in the shared placentae. The information obtained may help inform obstetric management. ^{[1, 2, 3, 4, 5, 6, 7]}

After birth, premature infants may need to undergo transcranial ultrasonography, as premature twins are susceptible to intraventricular hemorrhage and periventricular leukomalacia. Echocardiography may depict myocardial dysfunction, myocardial hypertrophy, valvular insufficiency, and/or pericardial effusions in either twin. Renal ultrasonography may depict altered renal echogenicity, which indicates hypoxic-ischemic cortical necrosis. Infants with hydrops may also need to be examined with abdominal sonography to detect ascites due to hydrops.

Conventional radiography has no role in the diagnosis or management of TTTS. A chest radiograph is sometimes required to detect pleural effusions and cardiomegaly in hydrops fetalis. Magnetic resonance imaging (MRI) is potentially useful in preoperative planning. Virtual navigation during fetal surgery is now possible as a result of shortened MRI acquisition times and volume-rendering software. Both Computed tomography (CT) scanning and MRI can be used in neonates to diagnose cerebral complications of TTTS.

 See the images below.

Perinatal outcomes improve with serial amniocentesis, with survival rates of 37-83%, though the complication rate from large amniocentesis is 1.5-8%. Ultrasonographic findings include discordance in fetal weight, discordance in the volume of amniotic fluid, fetal hydrops, disparity in the relative size and number of cord vessels, a single placenta with areas of disparity in the echogenicity of the cotyledons supplying the 2 cords, same-sex fetuses, and an inability to visualize the donor’s bladder while the recipient’s bladder is enlarged. ^{[8, 9]}

Vanderbilt and associates studied 262 consecutive laser-treated twin-to-twin transfusion syndrome patients with an objective to identify risk factors for cerebral lesions among survivors of twin-to-twin transfusion syndrome treated with laser surgery. This cohort showed low rates (4-7%) of severe neonatal cerebral lesions, with prematurity being the primary risk factor. ^[10]

Quintero et al developed a staging classification of TTTS based on clinical and sonographic criteria. ^[11] The stages of TTTS defined by using the proposed criteria have prognostic significance. This staging system may allow for a comparison of outcome data of TTTS with different treatment modalities.

TTTS is staged as follows:

Stage I – The bladder in the donor twin is still visible.

Stage II – The bladder in the donor twin is no longer visible, but no critically abnormal findings are observed on Doppler studies.

Stage III – Doppler studies are critically abnormal.

Stage IV – Hydrops is present.

Stage V – The demise of 1 or both twins has occurred.

Severe TTTS is defined as the presence of polyhydramnios (maximum vertical pocket of at least 8 cm) and oligohydramnios (maximum vertical pocket of less than 2 cm). Nonvisualization of the bladder in the donor twin with or without hydrops is noted. The middle cerebral artery, umbilical artery, ductus venosus, and umbilical vein in both fetuses are assessed with pulsed Doppler sonography. Critically abnormal Doppler studies are defined as absent or reversed end-diastolic velocity in the umbilical artery, reversed flow in the ductus venosus, or pulsatile flow in the umbilical vein.

Luks et al studied the feasibility of preoperative planning with MRI and computerized volume rendering in TTTS. ^{[12, 13, 14]} They examined 2 patients after TTTS was sonographically diagnosed and the indications for intervention were confirmed. The 2 patients had anterior placentas and underwent MRI without the need for maternal or fetal sedation. Three-dimensional (3D) and volume rendering were performed by computerized data and surgical-navigation software.

In both patients, a virtual rendering of the fetuses, placenta, and uterus could be manipulated to expose all sides, to demonstrate the location of the intertwin membrane, and to plan the point of entry and the curve of the endoscopic instruments. The results indicated that preoperative planning and virtual navigation are now possible in fetal surgery because of shortened MRI times and volume-rendering software.

Ultrasonographic features of twin-to-twin transfusion syndrome (TTTS) include the following (see also the images below) ^[1] :

Monochorionic (MC) twins with a single placenta, with visualization of a separating membrane

Same-sex fetuses

Midtrimester polyhydramnios-oligohydramnios sequence in the absence of other causes of an abnormal volume of amniotic fluid ^[15]

Discordance in fetal size, with the larger twin in the polyhydramnios sac and the smaller twin stuck against the uterine wall

Weight discordance between the fetuses, which may be 20% or more

In addition, the donor’s bladder may not be visualized, whereas the recipient’s bladder may be enlarged. The classic image of the stuck twin is that of 1 twin “plastered,” or stuck, at the front of the uterus (see the image below). By gravity, that twin should fall downward. Even if the mother’s position is changed, the stuck twin remains in the same position. ^{[16, 2, 3, 4, 5]}

Folding of the intertwin membrane occurs in about 25% of MC twins, ^[17] and about half of these twins subsequently develop severe TTTS. Another finding is an abnormal Doppler systolic-diastolic (S/D) ratio at the umbilical cord, which is absent end-diastolic flow in the donor’s umbilical artery accompanied by venous pulsation in the recipient’s umbilical vein. This sign is usually associated with a poor prognosis. On the contrary, the antenatal detection of artery-to-artery anastomosis is predictive of improved perinatal and double survival in TTTS, independent of the stage of disease. ^[18]

Hydrops or evidence of congestive cardiac failure may be seen in either twin but is most common in the recipient twin.

About 15% of MC twins with arterioarterial anastomoses develop TTTS. ^[19] Sebire et al reported that an increased thickness of the nuchal translucency at 10-14 weeks of gestation is a predictor of severe TTTS. ^[20] This finding demonstrated the underlying hemodynamic changes associated with TTS.

Senat et al assessed the value of the peak systolic velocity of the middle cerebral artery in predicting anemia within 24 hours of the death of 1 MC twin in TTTS and to correlate this velocity with hemoglobin concentration in fetuses at risk for acute anemia. ^[21] In such fetuses, the peak systolic velocity of the middle cerebral artery was a reliable and noninvasive diagnostic tool and may be helpful in counseling and planning for invasive assessment. The sensitivity and specificity were both 90%, with a false-negative rate of 10%.

The cocoon sign is present in at least 15% of patients with TTTS. Its recognition is important to prevent a misdiagnosis of TTTS. The cocoon sign is diagnosed when sonograms show a donor twin with severe oligohydramnios that is enveloped by dividing membranes and connected to the uterine wall by a laminar stalk of these membranes. ^{[22, 6]}

In TTTS, the recipient twin has progressive biventricular hypertrophy with predominant right ventricular systolic and biventricular diastolic dysfunction. Despite amnioreduction, the cardiovascular disease persists and even progresses in many recipient twins. ^{[23, 24]}

De Vries et al described 2 patients with lenticulostriate vasculopathy associated with TTTS. Lenticulostriate vasculopathy can be seen in an increasing number of clinical conditions, among which congenital infections and chromosomal abnormalities are best known. On transfontanelle sonography, the small arteries supplying the basal ganglia are indistinct from the brain parenchyma in normal infants. Bright, linear branched-candlestick stripes in these regions suggest lenticulostriate vasculopathy. ^[25]

Sonography is useful in predicting placentation, a process that may be helpful in predicting fetal outcome. In severe cases, the diagnosis of twin-to-twin transfusion syndrome (TTTS) is generally straightforward when imaging shows a single placenta with massive polyhydramnios in the sac of the recipient twin and a stuck donor twin attached to the uterine wall. Poor mobility and obvious growth discordance are often present. Mild forms may be difficult to diagnose because of the lack of uniform criteria. However, this possibility should be suspected whenever the amniotic fluid differs between the amniotic cavities regardless of the weight discordance between the twins.

The overall sensitivities and specificities of spectral and color Doppler ultrasonography in MC twins for in vivo detection of arterioarterial anastomoses are 85% and 97.3%, respectively. Detection rates increase with late gestations, with anterior placentas, and with large-diameter arterioarterial anastomoses. When arterioarterial anastomoses are identified, 15% of pregnancies develop TTTS, as compared with 61% when no arterioarterial anastomoses are seen (odds ratio, 8.6).

False-positive diagnoses are possible with twin oligohydramnios-polyhydramnios sequences and dichorionic twin pregnancies with fused placentas and growth retardation.

Maruotti GM, Saccone G, Morlando M, Martinelli P. First-trimester ultrasound determination of chorionicity in twin gestations using the lambda sign: a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2016 Jul. 202:66-70. [Medline].

Gallot D, Saulnier JP, Savary D, Laurichesse-Delmas H, Lemery D. Ultrasonographic signs of twin-twin transfusion syndrome in a monoamniotic twin pregnancy. Ultrasound Obstet Gynecol. 2005 Mar. 25(3):308-9. [Medline].

Vettraino IM, Hoprasart NJ, Bronsteen RA, Comstock CH. Clinical implications of the prenatal sonographic finding of fetal myocardial echogenic foci. J Ultrasound Med. 2005 Feb. 24(2):195-9. [Medline].

Denbow ML, Battin MR, Cowan F, et al. Neonatal cranial ultrasonographic findings in preterm twins complicated by severe fetofetal transfusion syndrome. Am J Obstet Gynecol. 1998 Mar. 178(3):479-83. [Medline].

Denbow ML, Cox P, Talbert D, Fisk NM. Colour Doppler energy insonation of placental vasculature in monochorionic twins: absent arterio-arterial anastomoses in association with twin-to-twin transfusion syndrome. Br J Obstet Gynaecol. 1998 Jul. 105(7):760-5. [Medline].

Quintero RA, Chmait RH. The cocoon sign: a potential sonographic pitfall in the diagnosis of twin – twin transfusion syndrome. Ultrasound Obstet Gynecol. 2004 Jan. 23(1):38-41. [Medline].

Duryea EL, Happe SK, McIntire DD, Dashe JS. Sonography interval and the diagnosis of twin-twin transfusion syndrome. J Matern Fetal Neonatal Med. 2016 May 16. 1-5. [Medline].

Roberts D, Neilson J, Kilby M, Gates S. Interventions for the treatment of twin-twin transfusion syndrome. Cochrane Database Syst Rev. 2008. (1):CD002073. [Medline].

Rossi AC, D’Addario V. Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of literature. Am J Obstet Gynecol. 2008 Feb. 198(2):147-52. [Medline].

Vanderbilt DL, Schrager SM, Llanes A, Chmait RH. Prevalence and risk factors of cerebral lesions in neonates after laser surgery for twin-twin transfusion syndrome. Am J Obstet Gynecol. 2012 Oct. 207(4):320.e1-6. [Medline].

Quintero RA, Morales WJ, Allen MH, et al. Staging of twin-twin transfusion syndrome. J Perinatol. 1999 Dec. 19(8 Pt 1):550-5. [Medline].

Luks FI, Carr SR, Ponte B, et al. Preoperative planning with magnetic resonance imaging and computerized volume rendering in twin-to-twin transfusion syndrome. Am J Obstet Gynecol. 2001 Jul. 185(1):216-9. [Medline].

Boyle M, Lyons A, Ryan S, Malone F, Poran A. Postnatal MRI Brain in Infants Treated for Twin-Twin Transfusion Syndrome. Ir Med J. 2015 Sep. 108 (8):240-3. [Medline].

Gomes Neto O, Marins M, Botelho RD, Nivoloni RC, Saura GE, Vessoni Arias A, et al. Feasibility and reproducibility of diffusion-weighted magnetic resonance imaging of the fetal brain in twin-twin transfusion syndrome. Prenat Diagn. 2014 Dec. 34 (12):1182-8. [Medline].

Lachapelle MF, Leduc L, Cote JM, et al. Potential value of fetal echocardiography in the differential diagnosis of twin pregnancy with presence of polyhydramnios-oligohydramnios syndrome. Am J Obstet Gynecol. 1997 Aug. 177(2):388-94. [Medline].

Adegbite AL, Castille S, Ward S, Bajoria R. Prevalence of cranial scan abnormalities in preterm twins in relation to chorionicity and discordant birth weight. Eur J Obstet Gynecol Reprod Biol. 2005 Mar 1. 119(1):47-55. [Medline].

Sebire NJ, D”Ercole C, Carvelho M, et al. Inter-twin membrane folding in monochorionic pregnancies. Ultrasound Obstet Gynecol. 1998 May. 11(5):324-7. [Medline].

Tan TY, Taylor MJ, Wee LY, Vanderheyden T, Wimalasundera R, Fisk NM. Doppler for artery-artery anastomosis and stage-independent survival in twin-twin transfusion. Obstet Gynecol. 2004 Jun. 103(6):1174-80. [Medline].

Taylor MJ, Denbow ML, Duncan KR, et al. Antenatal factors at diagnosis that predict outcome in twin-twin transfusion syndrome. Am J Obstet Gynecol. 2000 Oct. 183(4):1023-8. [Medline].

Sebire NJ, D”Ercole C, Hughes K, et al. Increased nuchal translucency thickness at 10-14 weeks of gestation as a predictor of severe twin-to-twin transfusion syndrome. Ultrasound Obstet Gynecol. 1997 Aug. 10(2):86-9. [Medline].

Senat MV, Loizeau S, Couderc S, et al. The value of middle cerebral artery peak systolic velocity in the diagnosis of fetal anemia after intrauterine death of one monochorionic twin. Am J Obstet Gynecol. 2003 Nov. 189(5):1320-4. [Medline].

Michelfelder E, Gottliebson W, Border W, Kinsel M, Polzin W, Livingston J. Early manifestations and spectrum of recipient twin cardiomyopathy in twin-twin transfusion syndrome: relation to Quintero stage. Ultrasound Obstet Gynecol. 2007 Dec. 30(7):965-71. [Medline].

Barrea C, Alkazaleh F, Ryan G, McCrindle BW, Roberts A, Bigras JL. Prenatal cardiovascular manifestations in the twin-to-twin transfusion syndrome recipients and the impact of therapeutic amnioreduction. Am J Obstet Gynecol. 2005 Mar. 192(3):892-902. [Medline].

Cosmi E, Litta P, Andrisani A, Di Lenardo L, Fadda GM, Ambrosini G. Non-invasive diagnosis by Doppler ultrasonography of fetal anemia due to massive fetomaternal hemorrhage in a case of twin-twin transfusion syndrome treated with serial amnioreduction. Ultrasound Obstet Gynecol. 2005 Apr. 25(4):415-6. [Medline].

de Vries LS, Beek FJ, Stoutenbeek P. Lenticulostriate vasculopathy in twin-to-twin transfusion syndrome: sonographic and CT findings. Pediatr Radiol. 1995 Nov. 25 Suppl 1:S41-2. [Medline].

Kontopoulos E, Chmait RH, Quintero RA. Twin-to-Twin Transfusion Syndrome: Definition, Staging, and Ultrasound Assessment. Twin Res Hum Genet. 2016 Jun. 19 (3):175-83. [Medline].

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR Consultant Radiologist and Honorary Professor, North Manchester General Hospital Pennine Acute NHS Trust, UK

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR is a member of the following medical societies: American Association for the Advancement of Science, American Institute of Ultrasound in Medicine, British Medical Association, Royal College of Physicians and Surgeons of the United States, British Society of Interventional Radiology, Royal College of Physicians, Royal College of Radiologists, Royal College of Surgeons of England

Disclosure: Nothing to disclose.

Durre Sabih, MBBS, MSc, FRCP(Edin) Director, Multan Institute of Nuclear Medicine and Radiotherapy (MINAR), Nishtar Hospital, Pakistan

Disclosure: Nothing to disclose.

Shyam Sunder Radha Krishna Koteyar, MBBS, DNB, DMRD, FRCR Consultant in Radiology, Pennine Acute Trust, Manchester, UK

Shyam Sunder Radha Krishna Koteyar, MBBS, DNB, DMRD, FRCR is a member of the following medical societies: Royal College of Radiologists

Disclosure: Nothing to disclose.

Bernard D Coombs, MB, ChB, PhD Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand

Disclosure: Nothing to disclose.

Karen L Reuter, MD, FACR Professor, Department of Radiology, Lahey Clinic Medical Center

Karen L Reuter, MD, FACR is a member of the following medical societies: American Association for Women Radiologists, American College of Radiology, American Institute of Ultrasound in Medicine, American Roentgen Ray Society, Radiological Society of North America

Disclosure: Nothing to disclose.

Eugene C Lin, MD Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine

Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, Society of Nuclear Medicine and Molecular Imaging

Disclosure: Nothing to disclose.

Nigel Thomas, MBBS Vice-Chair, Manchester (North) Research Ethics Committee; Honorary Lecturer, Visiting Professor, University of Salford, UK

Disclosure: Nothing to disclose.

Imaging in Twin-to-Twin Transfusion Syndrome

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