Postmortem examination of fetus, infant or young child should be performed with a special approach, different from that of adult. The presence of anatomical malformations or developmental variations should be assessed and dissection should preserve the anatomic relationships.
Thus, the organs are usually dissected en-bloc. Doctors who perform postmortem examination on fetuses and infants, therefore, should have a good working knowledge of normal anatomy, to identify the abnormalities and preserve the anatomic relationship until a consultation can be obtained.
FACILITIES AND EQUIPMENT
The facilities and equipment needed to perform fetal autopsy should be adequate from adult autopsy and minimum requirements are:
- Camera for photographic documentation
- Scale with case serial number
- Good source of light
- Standard weighing scale and measuring tapes
- Sterile swabs sticks
- Sharp cutting blade, scissors, plain and toothed forceps, etc.
- Facility of portable X-ray machine in certain cases
Different measurements and observation are used to document either normal anatomy or various pathologic conditions. For a good practice, postmortem examination should always be documented with photographs. The external features routinely photographed include frontal views of entire body, close up of the face and side of head, as well as any other unusual features. Photographs provide an accurate record, not only for academic purpose but also for the occasional case in which re-evaluation of the external features is needed. In addition to pictures, abnormal features should be documented through measurements of structures that can be compared with reference standards.
Maceration (organ softening due to decomposition) is a confounding problem in fetuses that have been retained in-utero following death. The degree of autolysis is variable depending upon intra-uterine conditions. Careful examinations of gross and microscopic changes help to estimate the time of death. Despite deformation due to maceration, many malformations can be distinguished upon careful inspection.
All the relevant measurements – fetal head circumference, chest circumference at the level of nipple, abdominal circumference at level of umbilicus, length of fetus (such as crown-rump, crown-heel and foot) and total weight of body – should be documented. Any congenital anomalies and marks of treatment should also be recorded.
Examination of head and neck
Distribution and quality of hair over the head and rest of the body as well as distribution of vernix casceosa over the neck, skin fold of arm and thighs should be documented. The size of the fontanelles should be measured. Any soft tissue swelling over the scalp (caput succedaneum) should be described. The eyes, palpebral fissures, whether it can be opened or not, the size of pupils, color of iris and sclera should be examined. The size, shape and position of nose as well as patency of choana should be examined. Oral cavity should be examined by digital palpation for detection of any abnormalities. The size, shape and position of pinna as well as the patency of external auditory meatus should be documented. The position of trachea and size of thyroid gland, features of congenital anomalies, like anencephaly, cleft palates, choanal atresia, etc. should be described in detail. Any injuries that may have taken place during the delivery procedure should be documented.
Examination over chest and abdomen
The size and shape of the chest and abdomen including any abnormalities and symmetry, position of nipple, distribution of subcutaneous fat over chest and abdomen should be documented. Abdomen should be palpated for any mass, including enlarged lymph nodes, liver and spleen.
Position and patency of meatus in male genitalia should be examined and scrotum palpated for presence of testes and any other masses. In females, the position of the meatus and configuration and relative size of the labia and clitoris should be examined. Anal orifice should be inspected for position, patency and anomalies, like absence or atresia. Limbs should be examined for symmetry and muscle bulk.
In internal examination, all three cavities are opened, similar to adult autopsy. To open the chest and abdominal cavities, ‘I’ – incision is given, starting from symphysis mentii to pubic symphysis at mid-line and by passing left or right few centimeters at the level of umbilicus.
The skin, subcutaneous tissues and muscles are reflected off the chest and abdomen. Inspect abdominal cavity for any collection (fluid, blood etc.) or adhesion. Collections are measured in a calibrated jar or at the very least estimated, if calibrated jar is not available.
Before opening chest plate, if pneumothorax is suspected, the entire body is placed in a basin or big container and the whole body immersed in water to observe for any escape of air from thoracic incisions, through the intercostal space. The chest plate is removed by cutting cartilaginous part of the rib cage at the costo-chondral junctions.
The chest cavity is inspected for any collection, adhesion and anomalies. The origin and relative positions of the great arteries as they arise from the heart should be noted.
The orientation and position of the abdominal organs should be inspected in situ. In fetuses and young infants, the liver is relatively large, extending well across the midline. Position of the right hepatic lobe should be in the right upper quadrant. Examine the location of spleen over left upper quadrant just lateral to the stomach.
The caecum and appendix are fixed to the posterior peritoneal wall in the right lower quadrant by the end of second trimester. Position of both kidneys and adrenal glands should be noted on each side after coils of intestines have been reflected. The gonads should be located and in females, the shape and position of the uterus between the bladder and rectum ascertained.
For premature males, intra-abdominal testes should be removed before evisceration. The umbilical arteries can be identified coursing along either side of the bladder. When the positions of the organs have been determined, the organs can be eviscerated in anatomically related groups (Ghon method) or all together en-bloc (Letulle method). The entire block from tongue to rectum can be removed, as in adults.
Both the thoracic and abdominal organs are removed in single block by detaching from its posterior attachments. The large veins and arteries of the neck should then be carefully dissected and identified, starting from the heart. These vessels should not be cut until all have been identified.
Before thoracic organs are removed, thymus should be carefully dissected from the pericardium, by elevating the thymus from the mediastinum. Before cutting any major vessels, the pericardial sac is cut opened and trimmed of free parietal pericardium.
A block is placed underneath the shoulder blades, causing hyperextension of the neck, and easing the release of tongue and dissection of neck structures. The tongue is released from the oral cavity by cutting in U-shape fashion from its attachment over the mandible. By holding tip of tongue, it is pulled outwards and downwards and released from its posterior attachment by cutting with a sharp blade. Then the large arteries and veins should be carefully dissected. The complete thoracic structure can be pull down to the level of diaphragm.
The remaining abdominal organs should be removed by cutting on both sides of the diaphragm, and moving coils of intestine to one side to release posterior peritoneal attachments. The entire bloc can be removed after separating from the level of rectum and anal canal.
Separation of the organ blocks
After the entire block has been eviscerated (using the Letulle method), the dorsal or posterior aspects of the block are examined by cleaning with clear running water. The descending aorta is lifted, transected, and opened vertically until its terminal branches along the posterior wall. Next, the diaphragm is reflected and separated to remove adrenal glands from the upper pole of kidneys.
The whole block is turned over to examine the ventral or anterior aspect. The procedure is slightly different from dissection in adults. The heart and lungs are separated from rest of the block by cutting along the inferior vena cava, esophagus, descending aorta at the level of diaphragm. This approach maintains the relationship of pulmonary arteries, ductus arteriosus and arch of aorta to the heart as well as of the esophagus with trachea.
The coils of small intestines are separated from its mesenteric attachments at ligament of Treitz up to the upper segment of rectum. Both ends of stomach (esophageal end and pyloric end) are either clamped or ligated before its separation. The whole length of intestine is examined for any malformations.
The patency of the biliary tree can be assessed by manually expressing bile from the gall bladder. Gall bladder is examined after separation from the liver. The liver is separated from diaphragm. The Spleen is separated from the hilum and removed.
The remaining block consists of the part of esophagus, stomach, duodenum and pancreas. The pancreas is removed from the stomach bed and dissected. In males, the testes are examined by removing them through the inguinal canal. In female, the uterus with ovaries are dissected from pelvic floor for examination.
Dissection of organs after evisceration
While preferable to examine the heart and lungs following overnight perfusion with formalin, social and cultural norms dictate quick release of the body and fixation of organs may not be feasible.
Dissection of The thoracic Block
The esophagus is cut open from posterior aspect and the trachea and larynx from anterior aspect thus preserving any tracheo- esophageal anomalies. The lungs are separated from its hilum.
Dissection of the heart
There are various methods of dissecting the heart to study the pathological lesions. For academic purposes, the best method is to open the heart chamber along the lines of normal flow of blood.
First, the right atrium is opened by a separate long axis incision infero-laterally to avoid the orifice of the inferior vena cava. This allows for inspection of the ostium of the coronary sinus and the oval fossa and the tricuspid valve. The patency of the connection between the atrium and right ventricle should be examined by use of a probe or finger.
The ventricle is opened by continuing the atrial incision through the atrioventricular valve and into the ventricle along the inferior aspect, parallel to the interventricular groove to the apex. Then the patency of pulmonary valve is examined using a probe, and the out flow tract is opened by continuing the same incision from the apex into the main pulmonary artery.
On the inferior aspect of the heart, the left atrium is incised in Y- shape to show the connection of the pulmonary veins with the left atrial cavity and to expose the mitral valve. After the patency of mitral valve is assessed, the incision should be carried along the inferior surface through the valve and the left ventricle to the apex, parallel to the interventricular septum. The incision is continued along the septum over the anterior aspect of left ventricle by using anterior descending coronary artery as a landmark.
For histologic examination, one section from each side of the heart, including atrium, ventricle, atrioventricular valve, and coronary artery, should be taken along the inferior incisions; papillary muscle sections from the right and left ventricles may also be collected. In cases with cardiac defects, the heart is kept together with the lungs en bloc and sections for histology taken judiciously to preserve the educational value of the gross specimen.
Dissection of lungs
Until the proper anatomical relationship between heart and lungs has been established, the lungs should not be separated from the heart. After complete examination of the size, shape, color and volume of both lungs, each lungs is dissected and weighed.
Hydrostatic Flotation Test
In order to determine whether the child was stillborn and liveborn, flotation test may be carried out by placing lungs in bucket full of water. There are five steps to the test:
- The entire thoracic block with the Heart and both lungs still attached is placed in water
- Each lung is dissected at the hilum and the heart is detached from the root of aorta and all three organs placed in water
- Each lung is dissected into lobes and all lobes are placed in water
- Each lobe is further dissected into 2-3 pieces and all pieces placed in water
- Each piece is then squeezed, ideally by placing between two sheets of paper and standing on it, and then all pieces are placed in water
Liver is used as a control and should be added to each step. If the lungs float on all five steps, Hydrostatic test is said to be positive, indicating respired lungs, provided the liver sinks in each step. If the liver floats as well, Hydrostatic test is said to be false positive, indicating decomposition. Hydrostatic test may also be false positive in cases of resuscitation.
If the lungs sink in all steps, Hydrostatic test is said to be negative, indicating non-respired lungs. Hydrostatic test may be false negative in case of pneumonia and atelectasis.
Dissection of abdominal organs
The separated liver and spleen should be sliced along the long axis, parallel to their inferior surfaces. This preserves the major vessels in liver and hilum in spleen. Umbilical vein, portal sinus and venous duct (ductus venosus) that are present over the inferior surface of the liver should be opened longitudinally.
The Pancreas is also dissected along the longitudinal plane. The capsules of kidneys are stripped to preserve generative glomeruli, and each kidney is dissected in half to expose the cortico-medullary area and renal pelvis. The patency of ureters should be examined by dissecting or probing. The urinary bladder should be cut open to examine for any anomalies. The testes should be dissected.
Examination of ossification centers
The skeletal system develops from multiple focii that enlarge and calcify to form bones. The human body has 806 centers of ossification during 11th – 12th of Intra-uterine life, which reduces to 450 centers at the time of birth and 206 bones in adult life. The appearance and fusion of these centers follow a sequential and chronological pattern and can be used to estimate the age of a new-born.
In a full term fetus or neonate, the ossification centers of importance include the sternum, the knee and the ankle. The sternum should be cut with a heavy knife at mid-line to expose the ossification centers. Similarly, lower end of femur and upper end of tibia as well as calcaneus, talus and cuboid are also cut to examine for appearance of ossification centers.
Dissection of Brain and spinal cord
The procedure for removal of brain from its cavity in fetus and infants is similar to that of adult autopsy, however, precaution should be taken while cutting the skull vault, especially if the superior sagittal sinus need to be preserved to examine for thrombosis.
A coronal incision is given over the scalp starting from one mastoid process to the other. The two halves of the scalp are reflected forwards and backwards, to expose the skull vault. Any caput or hemorrhage can be noted during scalp reflection. As the skull bone is thin in fetus, a sharp knife or heavy scissors can be used to cut open the skull.
In order to preserve the superior sagittal venous sinus and falx, it is better to cut 0.5cm on either side of the midline suture and the occipito-parietal sutures. This can be done by using a scalpel for the initial incision and extended using scissors. The coronal suture is cut across, and the frontal bone cut on each side to form two bony flaps. These two bone flaps can then be reflected downwards, with the dura matter attached, to allow for examination of the surface of the cerebral hemispheres. Any subdural or subarachnoid hemorrhage can be noted and the extent of the subarachnoid space assessed.
The brain is mobilized to examine the Falx Cerebri, tentorium, vein of Galen, and cerebrum. The anterior end of the Falx is incised and dissected backward and removed. The superior sagittal sinus can now be opened with scissors and examined for thrombus. Now brain can be removed in the same way as in adults; however, extra care is required owing to the fragility of the brain, particularly in a perinatal and/or macerated body.
The frontal lobes should be lifted away from the base of the skull and the optic nerves transected. Then internal carotid arteries, the pituitary, and the oculomotor nerves are transected on both sides. The temporal lobes should be eased away from the base of the skull and the tentoria cerebelli incised on both sides, either with scissors or scalpel. This will further separate the brain from the base of skull, exposing the brain stem. The medulla oblongata, the cranial nerves, and the vertebral arteries should be cut with a scalpel, as far distally as is possible.
Brain is removed by holding the occipital lobes with the left hand and gentle traction of brain stem with fingers of right hand. The remaining dural venous sinuses should then be incised with a scalpel and examined for thrombus. An initial examination of the brain should be made to assess the maturity of the gyri and to identify edema and /or herniation.
Cerebral hemisphere is separated from cerebellum and brain stem is separated from cerebellum by cutting cerebellar peduncle. Serial coronal section (1 cm thick) of cerebral hemisphere is dissected with the help of brain knife by placing convexities downwards on cutting board, starting from the frontal lobe and ending with the occipital lobe. In the same way, cerebellum and brain stem are also cut in the coronal plane.
Examination of the placenta
Examination of the placenta is a vital part of any fetal or perinatal post mortem. In any case of stillbirth, prematurity, or Intra uterine growth retardation, a sample of membranes and parenchyma can be taken, using sterile scalpel and forceps for bacteriology, if infection is suspected.
The cord length and site of insertion should be described as should any ruptures, varices, numbers of vessels and true knots. The fetal membrane is examined for meconium staining and discoloration indicating signs of infection. Point of rupture of sac and its size should be noted. The maternal cotyledons should be examined for their completeness. The membranes and cord should be separated and placental disc measured and weighed. Any blood clot received with placenta should be measured.
The placental disc is sliced at approximately 1 cm intervals. Any focal lesions, such as hematoma, infraction, thrombosis should be measured and noted. Sections of cord, membranes, and placental parenchyma should be taken for histological examination, in addition to any lesions identified macroscopically. In multiple pregnancy-associated placenta, the dividing membranes should also be carefully examined