The correlation between different human organs has been studied by means of automatic anatomy recognition, with model objects classified as sparse, non-sparse and hybrid . The delineation and recognition were easiest for non-sparse, i.e. compact, blob-like objects or entities. We can say that the objects of our study, the SM glands and pancreas belong to such a group. The mentioned study by Udupa et al  correlated the size among different objects within the thorax, the abdomen and the neck, but not mutually the soft tissue entities from different regions. Moreover, our study went into finer detail regarding the complete ductal systems of the SM and pancreas gland.
An autopsy retrospective study has presented correlation of different organ weights with the subjects’ age, body weight and height . The statistical analysis defined the age of 19 years as a cut-off point after which there are only individual variations, but no more general increases in organ weight. In line with this finding, we did not find it necessary to include the body height and weight in our analyses. However, we have measured the weight of the salivary glands and pancreas, and their values are within the normal limits reported previously [15,16].
It has been reported that age-related structural changes occur in salivary glands, with a reduction in volume of acini, and increase in the ductal volume, fibrous and fatty tissues, as well as lymphocytic infiltration . Comparable senescent changes have also been observed in the pancreas , but it was underlined that the pancreatic volume is stable until the 6th decade, and that severe pancreatic steatosis was demonstrated in those 60-69 years old. A number of pancreatic morphological abnormalities (calcification, atrophy, duct dilatation, pseudocyst) have been detected by digital autopsy, with highest frequencies from 6th decade onward . Our material comprised individuals from the younger-middle and middle age groups, and was carefully analyzed in sense of excluding all the cases with anamnestic data or observed pathology of both the pancreas and/or the submandibular glands.
Apart from aging, some fibroinflammatory conditions can also affect the salivary glands, such as the immunoglobulin G4-related disease , with bilateral swelling of glands and multiple enlarged cervical lymph nodes. Through medical history of our cases and detailed inspection during organ harvesting, we have not found such an entity in our material.
The projection images of the entire ductal system of pancreas can be achieved via endoscopic retrograde or magnetic resonance cholangiopancreatography (ERCP and MRCP). The non-invasive MRCP gives an image of lesser quality, and ERCP is thus considered to be the reference method . In cases of equivocal and mild pancreatitis, the appearance of abnormal side branches is highly important for early diagnosis . Likewise, the ductal properties of the salivary glands can be achieved by conventional, digital subtraction or MRI sialography [9,23].
Our methodology has focused both on the main duct and the side branches, as acinar destruction accompanied by fibrosis is a joint property of chronic inflammatory disease both for the pancreas and the salivary glands , and the entire size of the gland itself is a questionable parameter in discriminating the healthy and the diseased organ [9,25,26].
It has been noted that MPD and SMD anatomical features such as duct length and caliber can be implied in etiopathogenesis of different diseases, such as pancreatitis, sialolithiasis and sialadenitis [22,25]. Our first analysis applied to the length of the MPD and SMD. The two organs differ in the fact that more of a half of the SMD is situated extraglandularly, which is not the case with pancreas. The lack of correlation between the MPD and the full-length SMD can be attributed to the large range of variation of this parameter; when only the SMD intraglandular portion was taken into account, the correlation appeared as significant. A retrospective study of digital substraction sialograms found a mean value for SMD length of 58 mm , somewhat inferior to our measurements. The differences can be explained by a higher pressure of contrast injection in post-mortem specimens.
The caliber (internal diameter) of the MPD and the SMD is a valuable morphometric factor on which one can base the algorithm in clinical evaluation. It can be measured at different locations, such as head, body or tail in pancreas, or proximal, middle and distal third of the SMD [25,27]. Instead, we opted for one maximal caliber as being a more comparable feature. The median value for the MPD maximal caliber was close to the upper limit, but still with the normal ranges for the disease-free gland . In case of the SMD, the median maximal calibers we measured (2.6 mm and 2.3 mm) were also within the upper limits given by Horsburgh and Massoud , despite the methodological differences, i.e. post-mortem vs. digital subtraction sialography. However, in our study there was no correlation between the MPD and SMD maximal calibers.
Although the majority of interest within the two glands’ morphology has been focused on their principal excretory ducts [25,28], the MPD and SMD primary side branches have also been the objective of studies [9,22,29]. The vast majority of side branches open on each side of the main duct with very few on anterior and posterior walls . In our study, even those few ducts were visible as they do not take a geometrically ideal orthogonal course. It has been shown that irregularities of peripheral ducts, such as cystic dilations, ectasia and lack of opacification are signs of initial and mild inflammation. On the other hand, it must be underlined that non-invasive imaging has a lower rate of presenting these side branches, e.g. MRCP vs ERCP, or MR sialography vs. conventional or digital subtraction sialography [25,28,31]. Our post-mortem ductography achieved the complete arborization pattern, except in three submandibular glands. However, the correlation of side branches’ number was indeterminate, pancreas vs. left gland showed high significance, but pancreas vs. right gland did not, although it was close to the upper limit of significance. One of the plausible explanations for this can be found in the embryology of the MPD, which derives from the fusion of the ducts from ventral and dorsal pancreatic buds. The major part of MPD is derived from dorsal bud that composes the left (body-tail) part of postnatal pancreas.
Apart from the duct dimensions (length and caliber), the pattern of its course is also of diagnostic and therapeutic value. For instance, a tortuous MPD can pose technical difficulties for stent insertion , and a tortuous salivary duct can compromise balloon dilatation . With respect to the presence of ductal tortuosities, our study did not reveal an association between the pancreas and the salivary glands. Therefore, this feature can be ascribed to individual variability.
The left-right comparison of paired organs has also included the submandibular glands, mainly by measuring the cross-sectional or planimetric area occupied by the gland [1,34]. The detailed morphometry of the SMD ducts  did not, however, include the question of symmetry. Therefore, we carried out these analyses with regard to all the morphometric parameters observed (length, caliber, tortuosity, side branches of the SMD) and found full symmetry between the two sides.
Last but not least, we have observed cases with accessory submandibular ducts and lobes, not as an independent glandular structure , but mostly in the forms of outgrowths of the principal glands. This is in line with the embryology of the gland, where there is interaction between the endoderm and the neighboring mesenchyme, resulting in budding of the glands . Similar finding was not noted in pancreases.
This study has two limitations. One concerns the material sample with a predominance of males, and the other is a single measurement of dimensions rather than repetitive to obtain reproducibility of results.