Another serious shunt-related complication is subdural hematoma caused by too rapid reduction of ICP and size. This usually can be averted by careful assessment of ICP before insertion of the shunt and use of correct valvular pressure. Other complications that may occur include peritonitis, abdominal abscesses, perforation of abdominal organs by catheter or trochar (at the time of insertion), fistulas, hernias, and ileus. Children often need shunt lengthening as body growth occurs. This procedure usually involves replacing the distal catheter below the valve during the toddler period and again before the growth acceleration of puberty.