The early detection of local recurrence is one of the main goals of follow-up. Most relapses, when discovered, are either locally extensive or widespread disseminated, and occur, as mentioned, within a 2-year period from the initial "curative" operation. However, a small number of patients are in good general shape, with a surgically resectable recurrence, offering a chance for potentially curative resection.
Early detection of the local recurrence can be achieved by a combination of history, physical examination, CEA and Ca 19-9 measurements, endoscopy and imaging (CT, NMR, FGD-PET scan, ERUS) [41, 42]. In any clinical situation, there is frequently a single test that gives the physician the first hint of recurrent cancer.
Usual symptoms of a recurrent tumour are: pelvic pain (sometimes with radiation to lower extremities), rectal bleeding and change in bowel habits. For easier classification and assessment of treatment and prognosis, we can divide patients into groups according to symptoms as: S0, asymptomatic; S1, symptomatic, without pain; S2, symptomatic with pain .
It must be noted that a significant number of patients (around 50%) appear to be asymptomatic, despite evident recurrent tumour; certainly, if a patient complaints of a number of non-specific symptoms, the physician's index of suspicion should increase.
Physical examination can reveal a palpable mass within a minor pelvis. Digital examination may be very useful in detecting recurrence, which may be amenable to further surgery.
A review of symptoms and physical examination can reveal recurrence in 21% of cases .
Also, CEA level should be monitored regularly and its significant rise can lead to further investigations in early detection of local recurrence . The sen-sivity of the CEA serum test ranges from 43 to 98% (the ability to predict recurrence when the serum CEA is elevated pre-operatively); the specificity of a test is higher, ranges from 70 to 90% (not able to predict the recurrence if the serum CEA is normal pre-operatively. . Carlsson et al.  reported accuracy for CEA estimation of 84% if the upper limit was set at 7.5 ng/ml. Other Authors  defined an abnormal CEA assay as three progressively rising CEA values over post-operative baseline with at least one value over 10 ng/ml.
Computed tomography (CT) may provide useful anatomic information when evaluating hepatic metastases, but has limited accuracy in predicting resectability for cure because of its failure to detect other small lesions in the liver, or metastases elsewhere in the body . Also, the evaluation of CT scans should be taken with caution, because of a significant percentage of false-positive results in detecting recurrent disease, especially in the liver and the pelvis .
Magnetic resonance imaging (MRI) may be more sensitive than CT in detecting direct invasion of the sacrum in patients with pelvic tumor recurrence, but CT nor MRI are neither so successful in differentiating pelvic recurrence from post-operative fibrosis .
Fluorodeoxyglucose positron emission tomography (FDG-PET scan) is a relatively new, very useful procedure that exploits the increased rate of glycoly-sis in tumour cells (Fig. 3). It can successfully distinguish scar tissue from tumour tissue, which can prevent an unnecessary "second look" surgery . Schiepers et al.  compared CT and FDG-PET in the evaluation of 74 patients for recurrent colorectal
cancer and found specificity and sensitivity of FDG-PET to be much better (98% and 92%) than those of CT (60% and 72%).
A number of other diagnostic methods are available, and in some cases of crucial importance in deciding whether the patient is a candidate for curative procedure: barium enema, full lung tomography, intravenous pyelography (IVP), liver, spleen and bone scintigraphy.
Some new diagnostic tools are being evaluated, for example, carcinoembryonic antigen radioimmun-odetection of colorectal cancer recurrence. This is a method compatible to CT scan and potentially can help in avoiding more invasive diagnostic methods . Lechner et al.  report an overall accuracy of 91.6% in detecting recurrent colorectal cancer, which is superior to the results that could be obtained by the means of CT scan and/or endoscopy. Also, immunoscintigraphy detected more lesions in extra-hepatic areas, compared to CT scan.
In ideal circumstances a diagnostic laparoscopy could provide highly accurate information, and help in avoiding further, more invasive surgery. However, aside from its invasive nature, sometimes it is very difficult to explore all areas of interest without excessive manipulation.
When all other, non-invasive diagnostic methods fail to confirm the existence of highly suspectable recurrent tumor, "second look" surgery is indicated.
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