Ports are typically indicated for long-term venous access whose use can be defined as 'infrequent'. Typical example of infrequent use (that is, less frequently than once a week) is the use of venous access for chemotherapy every three weeks. In most of these cases, the most appropriate choice will be that of a totally implantable central venous system, or a 'port'.
The choice of a port involves two conditions: (a) that venous access is to be used for prolonged periods (longer than 4-6 months), and (b) that access is infrequent. In this sense, the use of the port for home parenteral nutrition (HPN) - which implies a daily use of the device or in any case for several days a week - should be seen as an exception (usually linked to a strong and motivated preference of the patient). The daily use of a port for HPN is associated with the risk of local complications of the skin over the reservoir and an increased risk of lumen occlusion due to lipid precipitation; also, such occlusion will be more difficult to disobstruct if compared to an external system. The theoretical advantage of the port in terms of infection prevention is completely nullified when the port is used every day (see the INS guidelines).
In children, the advantages of the port must be carefully weighed against the inevitable disadvantage of having to access the system each time through a puncture for positioning the Huber, a sting that can be well tolerated in the adult but which is often poorly tolerated in the child (especially if preadolescent), despite the use of anesthetic creams.
All the ports available on the market are central venous ports (i.e. with a tip positioned in the superior vena cava, or in the right atrium, or in the inferior vena cava): there are no 'peripheral' venous ports. Central access is, however, obtainable by puncturing and cannulating different veins, in the cervico-thoracic region (chest port), at the arm (PICC-port), or - very rarely - in the groin area (femoral port). The choice will be guided above all by venous availability. In general, even in the pediatric age, if the veins of the arm are adequate, the first choice will be a PICC-port.
The port's reservoir can be made of completely radiotrasparent material (plastic) or a mixture of plastic (resins of various types) and metal (usually, titanium); depending on the depth of the pocket, it will be possible to choose between standard reservoir (height about 12mm) or 'low profile' (about 10mm) or 'very low profile' (about 8mm); for PICC ports, the reservoir is 'very low profile'.
The catheter can be made of silicone or polyurethane, without significant difference in biocompatibility between the two materials. Evidence from the literature suggests avoiding valved catheters (greater risk of malfunction) and transparent silicone catheters (greater fragility). For PICC ports, polyurethane catheters should be preferred (easier to position). The diameter of the catheter (usually, 4- 6 Fr for the PICC ports, 6-7 Fr for the thoracic ports) must be proportionate to the diameter of the vein.