Yes, It is possible for constipation to inhibit urine flow. Because of constipation the impacted faecal mass in the large indestine will produce pressure symptoms over the underlying urinary bladder. So there may problem in contraction and relaxation of the bladder; this result in difficulty in emptying of bladder. Constipation may be caused by diet which are poor in fiber, so fiber rich diet such as Vegetable, fruits and bran should form part of the diet. Constipation may be caused by certain diseases such as underactive thyroid gland. Certain drugs such as aluminum hydroxide used for pepitic ulcer, cough syrup contains codeine may also produce constipation. If you are using these medicine it is preferable to substitute these medicine. Condition such obstruction of urinary bladder neck may also cause constipation. If your constipation is prolonged one better to rule out the above possiblities